samples FKM-251 to FKM-275

 

Check out the thin section scans introduction page for more information on the variety of samples featured here, how the scans were taken & processed for web display, and what additional optical and analytical data I hope to include in the figure captions as I continue to update the site and add to the collection of thin sections.

There’s also a fully searchable index covering the complete thin section set, listing for each sample its locality, the anticipated major minerals, a brief generalized geologic environment description, and where appropriate, the nature of any unusual element enrichments.

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essexite in thin section from Mont Johnson Canadaessexite in thin section from Mont Johnson Canada

left image: unpolarized light; right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-251 (billet from the Univ. Arizona petrology collection, sample Wards 32)
locality: Mont Saint-Gregoire (Mont Johnson; Monoir), Le Haut-Richelieu RCM, Montérégie, Québec, Canada.
rock type: essexite (nepheline monzodiorite).
major mineralogy: Plagioclase > orthoclase. Nepheline is interstitial to the feldspars and is abundantly flecked with tiny fibers (too small to quantitatively analyze) of what appears to be a Ca-dominant zeolite where Al:Si ≈ 1:1 (hence akin to a phase such as gismondine); interstitial patches of analcime are also present. The dominant mafic silicate present is ferri-kaersutite, intergrown with lesser amounts of a Ti+Fe3+-rich biotite and still lesser amounts of a sub-silicic Ti-rich clinopyroxene near the augite-diopside nomenclature boundary. The pyroxene and amphibole show essential no grain boundaries under BSE imaging (so the minor pyroxene is actually easier to spot under the petrographic microscope than under BSE), with the amphibole typically overgrowing the pyroxene, and in places a boundary of amphibole separates pyroxene from biotite. Within the larger clots of mafic minerals are also abundant large fluorapatite, magnetite (with a significant ülvospinel component; some magnetite crystals contain lamellae and coarser clots of ilmenite) and mildly-zoned titanite (with up to ~1.9 wt% Zr). Scattered zoned small zirconolite and rare baddeleyite round out the Zr-bearing assemblage. Scattered small pyrrhotite and rare pyrite are also observed.
accompanying videos: Short videos featuring the mineral associations and optical properties of the ferri-kaersutite in this thin section offer a more detailed look at this sample.

mineral representative mineral compositions in FKM-251
pyrrhotite Fe0.87S1.00
pyrite Fe1.00S2.00
baddeleyite not analyzed
ilmenite (Fe2+0.76Mg0.13Mn2+0.06Fe3+0.05)(Ti0.95Fe3+0.04V0.01)O3
magnetite
(most Mn2+-rich)
(Fe2+0.91Mn2+0.06Mg0.03)(Fe3+1.20Fe2+0.35Ti0.35Al0.09)O4
magnetite
(most Ti+Fe2+-rich)
(Fe2+0.98Mn2+0.01Mg0.01)(Fe3+1.04Fe2+0.46Ti0.46Al0.02Ca0.01)O4
magnetite (most Fe3+-rich;
adjacent to ilmenite)
(Fe2+0.95Mn2+0.03Mg0.02)(Fe3+1.53Fe2+0.20Ti0.20Al0.05V0.01)O4
zirconolite
(most Th+U-rich core)
(Ca0.82Th0.05Ce0.03U0.02La0.01Nd0.01Y0.01[HREE]~0.01)(Zr0.92Ti0.07Hf~0.01)
(Ti1.55FeT0.29Nb0.13Al0.03Ta~0.01MnT0.01)(O6.99F0.01)
zirconolite (middle) (Ca0.85Ce0.03Th0.02La0.01Nd0.01Y0.01[HREE]~0.01U0.01)(Zr0.95Ti0.04Hf~0.01)
(Ti1.65FeT0.24Nb0.09Al0.02Ta~0.01MnT0.01)(O6.99F0.01)
zirconolite
(most Ca+Zr-rich rim)
(Ca0.87Ce0.04La0.01Nd0.01Y0.01)(Zr0.98Ti0.01Hf~0.01)
(Ti1.68FeT0.22Nb0.10Al0.02Ta~0.01Si0.01MnT0.01)(O6.99F0.01)
fluorapatite (Ca4.93Sr0.02Na0.02Ce0.01FeT0.01)[P0.987Si0.01S0.003O4]3(F0.78[OH]0.20Cl0.01)
titanite (most Al+Fe-rich) Ca0.99(Ti0.89Fe3+0.04Al0.03Zr0.02V0.01)(O0.89[OH]0.06F0.05)[Si0.97Al0.03O4]
titanite (most Zr-rich) Ca0.99(Ti0.88Zr0.04Fe3+0.03Al0.02V0.01Nb0.01)(O0.92[OH]0.05F0.03)[Si0.97Al0.03O4]
augite (Ca0.88Na0.06Mg0.05Mn2+0.01)(Mg0.72Fe2+0.11Fe3+0.11Ti0.04Al0.01)[Si1.84Al0.16O5.99F0.01]
ferri-kaersutite
(most Mg-rich; main)
(Na0.73K0.26Sr0.01Ba0.01)(Ca1.80Na0.19Mn2+0.01)(Mg2.73Fe3+0.89Ti0.74Fe2+0.48Al0.12Mn2+0.03Zr0.01)
[Si6.14Al1.86O22](O1.48[OH]0.28F0.23Cl0.01)
ferri-kaersutite
(most Fe-rich; rim)
(Na0.68K0.32)(Ca1.82Na0.17Mn2+0.01)(Mg2.32Fe3+0.96Fe2+0.83Ti0.69Al0.14Mn2+0.05Zr0.01)
[Si6.04Al1.96O22](O1.38[OH]0.43F0.18Cl0.01)
“biotite” (K0.88Na0.06Ba0.010.05)(FeT1.26Mg1.10Ti0.36MnT0.030.25)[Si2.61Al1.28Fe3+0.11O10]([OH]1.16O0.72F0.11)
orthoclase (most K-rich) (K0.65Na0.30Ca0.03Sr0.01)[Si2.93Al1.07Fe3+0.01O8]
orthoclase (most Na-rich) (K0.58Na0.39Ca0.03Sr0.01)[Si2.92Al1.08Fe3+0.01O8]
“andesine”-dominant plag ss
(most Ca-rich cores)
(Na0.61Ca0.35K0.04Sr0.01)[Si2.59Al1.41Fe3+0.01O8]
“oligoclase”-dominant plag ss
(most Na-rich rims)
(Na0.71Ca0.22K0.03Sr0.01)[Si2.72Al1.27Fe3+0.01O8]
nepheline (Na2.60K0.54Ca0.14Sr0.010.71)[Si4.15Al3.82Fe3+0.03O16]
analcime (Na0.960.04)[Si1.97Al1.03O6] . H2O

 



olivine and chromite in thin section from Kiev Ukraineolivine and chromite in thin section from Kiev Ukraine

left image: unpolarized light; right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-252
locality: reportedly from “Kiev, Ukraine”. However, this locality is not entirely consistent with the sample’s purported combination of minerals; here an overview of the geology of Ukraine is instructive. Devonian and Permian evaporites in Ukraine form a belt in the east of the country, and Jurassic and Miocene evaporites form a sub-parallel belt in the west of the country, as well as a smaller exposure in the south near Kerch, Crimea (Hryniv et al., 2007) [← subscription required]. In contrast, running up through the center of the country (including in the vicinity of Kiev) is the 3.0 Ga Golovanevsk suture zone, which hosts a number of mafic-ultramafic bodies that also include chromatites (Gornostayev et al., 2004) [← subscription required]. So this being a chromite-bearing sample from the Kiev vicinity is certainly plausible. However, the possibility of boracite in this samples seems extremely unlikely.
rock type: apparently a chromatite clot in dunite.
major mineralogy: This specimen was labeled as “boracite with chromite”, and although the association of a chloro-borate typical of a sedimentary evaporite with a Cr-bearing spinel typical of an ultramafic igneous rock seems suspect, I was intrigued enough to purchase the sample (thinking, for example, that an ultramafic body could have intruded an evaporite). Although the billet is currently still out for thin section preparation, I prepared a small epoxy mount of the material to examine in advance. EPMA of this epoxy mount verifies abundant magnesiochromite and forsterite, with small amounts of Cr-enriched diopside. There is a widespread very low z Mg-silicate phase veining the olivine that seems inconsistent with either expected talc or serpentine (with an analytical total only 72 wt% and molar Mg:Si ≈ 11:4), so there is still some intrigue associated with this sample that will have to wait for resolution until the thin section comes back.

mineral representative mineral compositions in FKM-252
magnesiochromite (Mg0.66Fe2+0.33Mn2+0.01)(Cr1.51Al0.42Fe3+0.05Fe2+0.01)O4
forsterite Mg1.00(Mg0.90Fe2+0.08Ni0.01)[Si1.00O4]
diopside (Ca0.98Na0.01Mg0.01)(Mg0.94Fe2+0.02Cr0.02Al0.01Fe3+0.01)[Si1.97Al0.03O6]
low z Mg silicate? analysis pending

 



stillwellite in thin section from Dara-i-Pioz Tajikistanstillwellite in thin section from Dara-i-Pioz Tajikistan

left image: unpolarized light; right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-253
locality: Darai-Pioz glacier, Alai range, Tien Shan Mtns., Tajikistan.
rock type: highly-evolved B-rich alkali granite.
major mineralogy: specimen acquired for stillwellite-(Ce).

 



frolovite in thin sectionfrolovite in thin section

left image: unpolarized light; right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-254 (dealer sample number 1048)
locality: Solongo boron deposit, Buryatia, Transbaikalia region, Eastern Siberia, Russia.
rock type: calcic borate skarn.
major mineralogy: specimen acquired for frolovite. Sample FKM-284 is a similar olshanskyite-bearing calcium-borate skarn from the Titovskoe boron deposit.

 



zincohögbomite in thin section

left image: unpolarized light; right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-255 (dealer sample number 4372)
locality: Nežilovo, Veles, Macedonia.
rock type: metasomatized(?) marble.
major mineralogy: specimen acquired for zincohögbomite-2N6S.

 



ferri-leakeite in thin section

left image: unpolarized light; right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-256 (dealer sample number 3433)
locality: Arroyo de la Yedra, ~6 km NNE of Manzanares el Real, Eastern Pedriza Massif, Sierra de Guadarrama, near Madrid, Spain.
rock type: “episyenite”; desilicified and alkali-metasomatized (albitized) originally cordierite-bearing (peraluminous) granitoid.
major mineralogy: specimen acquired for ferriwhittakerite (however, see nomenclature/analytical note below). Amphibole in this sample occurs both as abundant small needle-like inclusions in quartz (one analysis of this habit showed a ferri-pedrizite to near ferro-ferri-pedrizite composition), and as a few scattered clusters of somewhat larger crystals (the “video” amphibole grains; see below). Some of these larger grains are weakly zoned in BSE, dominated by a main ferri-fluoro-leakeite composition, but with small external rims or internal patches (along cracks?) transitioning towards ferri-pedrizite to near ferri-fluoro-pedrizite. Others of these larger grains are not obviously zoned, but nonetheless also vary slightly in chemistry from grain to grain, from ferri-fluoro-leakeite to more slightly more OH-rich compositions just over the ferri-leakeite nomenclature boundary. The amphiboles are hosted in a rock composed of primarily weakly-zoned K-feldspar (orthoclase?), albite and quartz. Accompanying the clusters of amphibole are widespread small crystals of aegirine-augite locally grading into aegirine. Initial normalization of the clinopyroxene showed somewhat high Si (2.02 to 2.03 apfu Si) and uncharacteristically slightly low totals, and suggested that low but still significant levels of Li may also be present in the clinopyroxene. The addition of sufficient estimated Li (up to ~1500 ppm) improved the normalizations and totals, although independent confirmation is still necessary. Two micas are present: very sparse biotite, which may be a pre-metasomatic primary igneous mineral, and scattered metasomatic tainiolite. It is unclear if the biotite contains any significant Li, because, even more so than with the amphiboles, there are even fewer stoichiometry and charge balance constraints available for the micas to derive an unambiguous formula. Although without added Li the biotite analytical total is a bit low, it is not inconsistent with results from biotite from other rocks measured during the same session, more confidently presumed to be Li-free. A variety of minor accessory minerals are also present, including zircon, fluorapatite, titanite and an Fe-oxide too small to analyze. Additionally, several “clots” of zoned ferriallanite-(Ce) are intergrown with the amphibole/clinopyroxene clusters. As also previously noted with the clinopyroxene, initial normalization of these allanites (sensu lato) showed similar markedly high Si (3.08 to 3.09 apfu Si), under-filled ∑(VIM) cation sites and low analytical totals, all again suggesting unanalyzed Li may be present (and again requiring independent confirmation).

Note: former mixed-cation B(NaLi) amphiboles such as “ferriwhittakerite” have been reclassified by Hawthorne et al., 2012 into either B(NaNa) or B(LiLi) groups. Hence, this material is now presumably either a leakeite-root amphibole [B(NaNa) with Li primarily in CM], a pedrizite-root amphibole [B(LiLi) but with additional Li also in CM], or possibly a holmquistite-root amphibole [B(LiLi) without significant Li in CM], depending on whether the B-site is predominantly Na or Li, and if there is additional Li in the C-site. At least four distinct Li-essential species from among these root names are reported from among the Pedriza Massif amphiboles, and there are reportedly significant compositional variations even within zoned single crystals (so single crystals may span these and potential transitional species). Because of this variability, in-situ micro-analysis for Li by either SIMS or LA-ICP-MS/OES is necessary to properly characterize individual BSE-recognizable growth zones. However, if these these techniques are not available, plausible Li contents can be bracketed by stoichiometry-controlled lower and upper bounds, and within those ranges more precise values can be reasonably estimated from overall formula and analytical total constraints. Minimum Li is calculated using the amphibole normalization scheme ∑(Si+P+S+Ge+As) = 8, since sufficient Li must be added simply to completely fill the nominally vacancy-free [T+VIM+VIIIM] cation sites. Maximum Li is calculated using the amphibole normalization scheme ∑(all cations) = 16 while simultaneously maintaining ∑(Si+P+S+Ge+As) = 8 (in these analyses, ∑Al is close to 0); this normalization scheme moves Na from the VIIIM site to fill the XIIA site, then accommodating the new deficit in VIIIM with extra Li. Charge balance is maintained by converting a compensating amount of Fe3+ to Fe2+. Applied to the compositions here, although minimum Li gives seemingly viable (i.e. stoichiometric & charge-balanced) formulas, in most cases ∑M3+ >> ∑M2+, inconsistent with the typical expected VI(M2+2M3+2Li) site filling of leakeite (sensu lato) and pedrizite (sensu lato) root-name formulas; hence, the formulas derived from the minimum calculated Li contents don’t correlate to known amphibole end-members, and they can’t be named using the current amphibole nomenclature. In contrast, incorporating maximum Li gives both viable formulas and acceptable names, and results in better but still somewhat askew VIM site occupancies (in this case, ∑M3+ << ∑M2+). For the Li contents adopted here, estimated Li values between the minimum and maximum calculated values were selected to optimize the expected relationship M2+ ≈ M3+. In the couple of cases where this was not possible, estimated Li was selected to at least ensure Mn3+/∑Mn = 0. The resultant estimated Li values ended up approaching the maximum calculated value. Hence perhaps not unexpectedly, in all but two cases, the derived name using these estimated Li vales were the same as those derived from maximum calculated Li (except with maximum Li, point #63 becomes “ferri-pedrizite” and point #73 becomes ferro-ferri-pedrizite). Also, using sub-maximum Li estimates meant that the total [Na+K] XIIA site occupancies were typically around 0.6-0.8 apfu; these compare well to the published composition data for “ferriwhittakerite” (now ferri-leakeite) from the Pedriza Massif (Oberti et al., 2004). As an additional constraint, using the estimated Li values (and also including stoichiometric H2O), analytical totals for the series of amphibole analyses ranged acceptably between 100.1 and 101.4 wt%.

mineral representative mineral compositions in FKM-256
Fe-oxide/oxyhydroxide too small to analyze
fluorapatite (Ca4.87Na0.02Y0.02Sm0.01Mn0.01)[P0.997Si0.003O4]3(F0.97[OH]0.03)
zircon not analyzed
titanite (Ca0.97[REE]0.01)(Ti0.92Fe3+0.08Al0.01V0.01)(O0.94[OH]0.06)[Si1.00O4]
ferriallanite-(Ce)
(lower z zone)
(Ca0.99Na0.01)(Ca0.37Ce0.35La0.18Nd0.05Pr0.03Sr0.01Y0.01)(Fe3+0.91Al0.06Ti0.02)Al1.00
(Fe2+0.48Fe3+0.43Li0.07?Mn2+0.02)(O0.99F0.01)[Si2.00O7][Si1.00O4](OH)
ferriallanite-(Ce)
(higher z zone)
Ca1.00(Ce0.38Ca0.25La0.17Nd0.08Pr0.04Sr0.04Y0.03Sm0.01[HREE]0.01)(Fe3+0.82Al0.17Ti0.01)Al1.00
(Fe3+0.51Li0.23?Fe2+0.22Mn2+0.03Mg0.01)O1.00[Si2.00O7][Si1.00O4](OH)
aegirine-augite-dominant
cpx ss (small patches;
most [Ca+Fe2+]-rich)
(Ca0.52Na0.43Li0.05?)(Fe3+0.46Fe2+0.36Mg0.13Mn2+0.04Al0.01)[Si2.00O6]
aegirine-augite-dominant
cpx ss (main;
most [Na+Fe3+]-rich)
(Na0.59Ca0.36Li0.05?)(Fe3+0.62Fe2+0.25Mg0.09Mn2+0.04Al0.01)[Si2.00O6]
aegirine-dominant cpx ss
(small patches)
(Na0.91Ca0.08Li0.01?)(Fe3+0.89Fe2+0.03Mg0.03Mn2+0.02Al0.01Ti0.01)[Si2.00O6]
ferri-fluoro-leakeite dominant
B([NaNa]/[LiLi])-amph ss
(#60; video grain 1, main z)
(Na0.47K0.190.34)(Na1.87Ca0.08Li0.05)(Mg2.09Fe3+1.88Li0.71Mn2+0.16Ti0.07Al0.06Zr0.01Zn0.01)
[Si8.00O22](F1.00[OH]0.86O0.15)
ferri-fluoro-pedrizite/
ferri-pedrizite boundary
B([NaNa]/[LiLi])-amph ss
(#61; video grain 1,
weakly higher z area)
(Na0.67K0.010.32)(Li1.44Na0.55Ca0.01)(Fe3+1.86Mg1.19Fe2+0.83Li0.80Al0.23Mn2+0.07Zn0.01)
[Si8.00O22]([OH]1.01F0.98O0.01)
ferri-fluoro-leakeite dominant
B([NaNa]/[LiLi])-amph ss
(#62; video grain 2,
main core z; most Mg-rich)
(Na0.49K0.150.36)(Na1.41Li0.51Ca0.08)(Mg2.21Fe3+1.83Li0.61Mn2+0.16Ti0.12Al0.05Zn0.01)
[Si8.00O22](F1.08[OH]0.69O0.23)
ferri-fluoro-leakeite/
ferri-leakeite boundary
B([NaNa]/[LiLi])-amph ss
(#63; video grain 3,
most OH-rich)
(Na0.43K0.150.42)(Na1.30Li0.62Ca0.09)(Fe3+1.97Mg1.30Li0.78Fe2+0.73Al0.12Mn2+0.06Ti0.02)
[Si8.00O22]([OH]0.98F0.96O0.01)
ferri-fluoro-leakeite dominant
B([NaNa]/[LiLi])-amph ss
(#65; video grain 4, main z)
(Na0.49K0.190.32)(Na1.37Li0.55Ca0.08)(Fe3+1.93Mg1.44Li0.84Fe2+0.53Al0.10Mn2+0.06Ti0.05Zr0.02)
[Si8.00O22](F1.27[OH]0.64O0.09)
ferri-fluoro-leakeite dominant
B([NaNa]/[LiLi])-amph ss
(#64; video grain 4, weakly
lower z area; most F-rich)
(Na0.62K0.190.19)(Na1.51Li0.41Ca0.08)(Fe3+1.88Mg1.62Li0.91Fe2+0.29Al0.12Mn2+0.09Ti0.06)
[Si8.00O22](F1.54[OH]0.34O0.12)
ferri-pedrizite dominant
B([NaNa]/[LiLi])-amph ss
(#73; needle clusters in quartz)
(Na0.68K0.010.31)(Li1.52Na0.46Ca0.02)(Fe3+1.83Mg1.09Fe2+0.92Li0.81Al0.26Mn2+0.07Ti0.02Zn0.01)
[Si8.00O22]([OH]1.16F0.81O0.03)
“biotite” (appears to be
pre-metasomatic & so
assumed to be Li-free)
(K0.950.05)(FeT1.16Mg0.86Al0.56Ti0.15MnT0.02Zn0.010.24)
[Si2.81Al1.19O10]([OH]1.53O0.30F0.16)
tainiolite (K0.94Na0.010.05)(Mg1.78Li1.00FeT0.12Al0.05Ti0.03MnT0.02)
[Si3.99Al0.01O10](F1.87[OH]0.07O0.06)
quartz not analyzed
K-feldspar (orthoclase?)
(main; most K-rich)
(K0.94Na0.05Ba0.01)[Si2.97Al1.03P0.01O8]
K-feldspar (orthoclase?)
(higher z wisps; most Ba-rich)
(K0.91Na0.06Ba0.03)[Si2.97Al1.02O8]
albite (Na0.91K0.06Ca0.04)[Si2.94Al1.06O8]

accompanying videos: Short videos featuring the mineral associations and optical properties of the ferri-fluoro-leakeite in this thin section offer a more detailed look at this sample.

mineral PPL (lower
polar rotation)
PPL
(stage rotation)
XP
(stage rotation)
optic figure
(stage rotation)
ferri-fluoro-leakeite
PPL: deep blue-violet/greenish-blue/greenish-yellow pleochroism, high relief;
XP: up to 1st order purple δ, with anomalous blue and brown overtones in optic axis sections;
with aegirine-augite, quartz and alkali feldspar (100X)

 



chromceladonite in thin section

left image: unpolarized light; right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-257 (dealer sample number 3002)
locality: Srednyaya Padma mine, Velikaya Guba uranium-vanadium deposit, Zaonezhie peninsula, Lake Onega, Karelia Republic, Russia.
rock type: sample is a U-V-metasomatite metamorphosed to greenschist facies (Borozdin et al., 2013).
major mineralogy: specimen acquired for chromceladonite. Chromceladonite is indeed noted in the sample, but additional analyses across the sample also show other mica compositions that are relatively low in Cr but variably V-enriched. These additional compositions range from what appears to be an approximately dioctahedral “vanadioceladonite”, to a more Mg-rich ambiguously “dioctahedral/trioctahedral” mica along a join between “vanadioceladonite” and phlogopite. These V-enriched compositions were initially thought to be roscoelite (which is noted at the locality), but in these analyses the V content is too low and is also subordinate to Mg. It is also not clear at the moment how these different compositions are distributed in the sample, since they appear optically similar and differ only subtly in BSE; X-ray mapping for Cr, V, and Mg should ascertain whether these are randomly sampled zoned crystals, randomly sampled intergrowths of separate minerals, or if these compositions are spatially-controlled and characteristic of the local mineralogy where the micas were sampled. Indeed, the overall rock is somewhat heterogeneous in nature, with some areas of the sample largely composed of of patchy fine-grained essentially indeterminable Fe+(Ti+V+Cr)-oxide(s)/oxy-hydroxide(s) admixed with quartz, while other areas are almost mono-mineralic mica(s) accompanying rounded quartz that may represent original detrital material. Two main abundant opaque oxides are present throughout the sample: (1) an equant “brighter BSE oxide” spinel group phase composed of weakly zoned boundary-composition Fe-rich zincochromite/Zn-rich chromite, and (2) a more elongate “darker BSE oxide” composed of what is presumably a markedly [V+Cr]-enriched hematite. An additional “darkest BSE” high-[Ti+Cr] oxide is also present, that compositionally somewhat resembles an unnamed oxide (UM2002-05-O:CrTiV) found in metamorphic rocks near Lake Baikal (however, the analytical total of the material here is low, at only ~93.4 wt%, suggesting the possibility of OH/H2O [so maybe be a chromian “leucoxene”?]). Small ratty patches of a mineral that normalizes well to a goethite-like [Fe+V+Cr]-oxyhydroxide are scattered around the other oxides. Minor sulfides are present in the sample, including galena (both alone and in one case complexly intergrown with chalcopyrite), sphalerite and pyrite. Minor small coffinite is present; the detection of low-level Ca and other elements in the coffinite analysis may indicate some sparse admixed Ca-U-silicate, or more likely represents contamination/overlap with adjacent material. Barite is abundant in the sample, and ranges from scattered thin stringers (visible in the BSE imaging as high-z “streaks”) to several large masses and large individual crystals; these are readily visible in the thin section scans as the colorless moderate relief crystals (regular light) with 1st order near-black, gray, and white birefringence (crossed polarizers view).

mineral representative mineral compositions in FKM-257
galena Pb1.00S1.00
sphalerite (Zn0.99Fe2+0.02)S0.99
chalcopyrite Cu1.01Fe0.99S1.99
pyrite Fe1.00S2.00
“(Cr,V)2Ti2O7“? or chromian “leucoxene”?
(see text)
~(Cr1.38Fe3+0.33V3+0.21Fe2+0.03Mg0.01)(Ti2.02Nb0.01)O7-x(OH)2x
total ~99 wt% when x = 1
hematite (most Fe-rich) (Fe3+1.59V3+0.17Cr0.16Ti0.03Fe2+0.03)O3
hematite (most [Cr+V]-rich) (Fe3+1.33V3+0.29Cr0.29Ti0.04Fe2+0.04)O3
chromite/zincochromite boundary
spinel ss (core)
(Fe2+0.49Zn0.49Mn2+0.01Mg0.01)(Cr1.02V3+0.38Fe3+0.29Si0.13Fe2+0.13Al0.04)O4
zincochromite-dominant
spinel ss (mantle)
(Zn0.52Fe2+0.46Mn2+0.01Mg0.01)(Cr0.91V3+0.53Fe3+0.53Al0.02)O4
goethite? (Fe3+0.47V3+0.36Cr0.11Al0.03)O(OH)
barite (Ba0.97Sr0.03)[SO4]
coffinite? ~(U0.81Ca0.13Ce0.02Nd0.02Fe3+0.02Sc0.01Zr0.01Y0.01)
[Si0.75V5+0.15Al0.01O~3.60(OH)~0.40]
chromceladonite (K0.93Na0.010.06)(Cr1.01Mg0.64FeT0.20Al0.17V3+0.05Ti0.02~0.89)
[Si3.58Al0.42O10]([OH]1.89F0.08O0.03)
“vanadioceladonite” (K0.980.02)(Mg0.91V3+0.61FeT0.33Al0.21Cr0.19Ti0.03~0.72)
[Si3.40Al0.60O10]([OH]1.74F0.19O0.07)
“vanadioceladonite”-phlogopite
join mica
(K0.960.04)(Mg1.63V3+0.35FeT0.33Cr0.15Al0.09Ti0.04~0.41)
[Si3.18Al0.82O10]([OH]1.61F0.31O0.08)
quartz not analyzed

 



ellenbergerite in thin section

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sample: FKM-258 (dealer sample number 4280)
locality: Case Parigi, Martiniana Po, Piedmont, Italy.
rock type: eclogite facies whiteschist.
major mineralogy: The specimen was acquired for P- and Zr-enriched ellenbergerite, which occurs as scattered crystals within a large mass of predominately pyrope. The ellenbergerite exhibits notable color zoning (independent of its inherent pleochroism), ranging from localized bands of deeper magenta (typically near crystal edges) to patches of very pale lavender (usually away from the edges). The source of the color is presumed to be Ti4+-Fe2+ charge transfer between adjacent sites. Although the estimation of Fe3+/∑Fe from a microprobe analysis alone is fraught with uncertainty, especially when total Fe is low, it is nonetheless compelling to note that the normalizations of analyses of the more strongly-colored portions are indeed Fe2+-dominant (and this Fe2+ was assigned to the Mg site), whereas those of the weakly-colored areas are Fe3+-dominant (and this Fe3+ was assigned to the [Mg+Ti+□] site). The more deeply colored zones also show Ti>Zr. Besides the ellenbergerite, crystals of kyanite (with pale blue pleochroism), rutile, and talc-clinochlore intergrowths are abundant within the pyrope. Minor clots of an additional sheet silicate, presumed to be a retrograde smectite-group mineral, are present and these contain inclusions of kyanite and a Na- and Al-bearing Mg-amphibole akin to the “sodicgedrite” of Leake et al., 1997 (or alternatively, represented by a composition along the gedrite-“rootname 1” join of Hawthorne et al., 2012 [see composition table]). Another amphibole, somewhat akin to a nearly Ca-free but VIIIMg-enriched winchite but really best described as a composition along the glaucophane-“rootname 7” join of Hawthorne et al., 2012, occurs as sparse scattered crystals within the pyrope. Sparse small “ratty” fluorapatite is also observed. This sample is from the same general vicinity as FKM-42, but has a more diverse mineralogy than the latter.
accompanying videos: Short videos featuring the mineral associations and optical properties of the ellenbergerite in this thin section offer a more detailed look at this sample.

mineral representative mineral compositions in FKM-258
rutile (Ti0.97Nb0.01Al0.01)O2
fluorapatite (Ca4.63Sr0.25Na0.02Ca0.01)[P0.997Si0.003O4]3(F0.61[OH]0.24Cl0.15)
pyrope (Mg2.93Fe2+0.06Ca0.01)(Al1.97Fe3+0.03)[Si0.977Al0.023O4]3
kyanite Al2.00O1.00[Si0.99Al0.01O4]
ellenbergerite (most P-rich;
quite strongly-colored)
(Mg5.94Fe2+0.06)(Mg0.78Ti0.46Zr0.14Al0.010.61)Al6.00[Si1.00O4]4[Si0.973P0.033O3(OH)]4([OH]5.99F0.01)
ellenbergerite (most Ti-rich;
most strongly-colored)
(Mg5.94Fe2+0.06)(Mg0.64Ti0.56Zr0.08Al0.070.65)Al6.00[Si1.00O4]4[Si0.983P0.018O3(OH)]4([OH]5.99F0.01)
ellenbergerite (most Zr-rich;
least strongly-colored)
Mg6.00(Mg0.57Zr0.38Ti0.29Fe3+0.050.71)Al6.00[Si1.00O4]4[Si1.00O3(OH)]4([OH]5.98F0.02)
gedrite-“rootname 1” join
B(MgMg)-orthoamph ss
(Hawthorne et al., 2012)
or “sodic-gedrite”
(Leake et al., 1997)
(Na0.550.45)(Mg1.80Fe2+0.19Ca0.01)(Mg3.71Al1.28Ti0.01)[Si6.29Al1.71O22]([OH]1.97F0.01Cl0.01O0.01)
glaucophane-“rootname 7” join
B([NaNa]/[NaMg])-amph ss
(Hawthorne et al., 2012)
(K0.010.99)(Na1.47Mg0.38Ca0.08Fe2+0.07)(Mg2.93Al2.06Ti0.01)[Si7.82Al0.17O22]([OH]1.94F0.05O0.01)
talc Na0.01(Mg2.79Al0.06FeT0.010.14)[Si4.02O10]([OH]1.95F0.05)
clinochlore (Mg4.60Al1.25FeT0.050.10)[Si2.92Al1.08O10]([OH]7.99F0.01)
“smectite” group mineral? (Na0.17K0.03Ca0.01)(Mg2.03Al0.65FeT0.010.31)[Si3.73Al0.27O10]([OH]1.98F0.01O0.01?)

 



emeleusite in thin section

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sample: FKM-259 (dealer sample number 6887)
locality: Illutalik Island, Narsaq, Kujalleq, Greenland.
rock type: aegirine, albite and narsarsukite-bearing peralkaline trachyte dyke.
major mineralogy: specimen acquired for emeleusite.

 



helvine in thin section

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sample: FKM-260 (dealer sample number 3429)
locality: Hørtekollen, Sylling, Lier, Buskerud, Norway.
rock type: magnetite-helvite skarn.
major mineralogy: specimen acquired for helvite, fluorite and tourmaline.

 



volkonskoite in thin section

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sample: FKM-261 (dealer sample number 4118)
locality: Although the general locality (probably within a 10 km radius) for this sample seems to be relatively well-established, a more precise locality is somewhat unclear. The sample is listed being from “Stone quarries”, ~70 km SE of Amman, Lisdan-Siwaga fault, Hashem region, Jordan. The Lisdan-Siwaga fault mindat locality entry is not especially precise and covers two listed sub-localities separated by about 20 km along the fault strike. However, the same dealer has more recently offered apparently identical material that is alternatively listed as from the nearby Transjordan Plateau, also ~70 km SSE from Amman. Sizable stone quarries are readily identifiable on Google Maps within ~3 km of this latter locality, although the actual Lisdan-Siwaga fault (and the nearest fault-hosted mindat entry, identified as the “quatranaite locality“), appears to be an additional 4-5 km further east. After evaluating this set of localities, perhaps the “best” locality in mindat may be that identified as Khan ez Zabid, also ~70 km SSE of Amman, because this location encompasses the preceding localities with a ~10 km error radius and also specifically includes volkonskoite as a reported mineral.
rock type: low temperature alteration of original pyrometamorphic sanidinite-facies phosphatic carbonates and bitumen-bearing (“oil”) shales.
major mineralogy: specimen acquired for volkonskoite (Cr-rich smectite).
accompanying videos: Short videos featuring the mineral associations and optical properties of the diopside in this thin section offer a more detailed look at this sample.

 



åkermanite in thin section

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sample: FKM-262 (dealer sample number 4146)
locality: Kovdor phlogopite mine (Slyuda mine), Kovdor massif, Russia.
rock type: melilitolite.
major mineralogy: specimen acquired for åkermanite and phlogopite.
accompanying videos: Short videos featuring the mineral associations and optical properties of the åkermanite in this thin section offer a more detailed look at this sample.

mineral representative mineral compositions in FKM-262
pyrrhotite (troilite?) Fe1.01S1.00
magnetite (Fe2+0.95Mg0.03Mn2+0.01Ni0.01)(Fe3+1.93Fe2+0.03Ti0.03)O4
forsterite (main; most Fe-rich) (Mg0.97Ca0.02Mn2+0.01)(Mg0.74Fe2+0.25)[Si1.00O4]
forsterite (most Mg-rich) (Mg0.99Ca0.01)(Mg0.85Fe2+0.14Fe3+0.01)[Si0.99Fe3+0.01O4]
monticellite (most Fe-rich) Ca1.00(Mg0.69Fe2+0.29Mn2+0.01)[Si1.00O4]
monticellite (most Mg-rich) (Ca0.98Mg0.01Mn2+0.01)(Mg0.78Fe2+0.22)[Si1.00O4]
andradite (most Al-rich) (Ca2.98Fe2+0.02)(Fe3+1.33Al0.55Ti0.07Mg0.04Fe2+0.01)[Si0.993Al0.007O4]3
andradite (most Fe-rich) Ca2.99(Fe3+1.60Al0.34Ti0.03Mg0.02)[Si0.997Al0.003O4]3
åkermanite (Ca1.74Na0.25Sr0.01)(Mg0.67Al0.24Fe2+0.08Fe3+0.01)[Si2.00O7]
diopside (Ca0.98Na0.01Mg0.01)(Mg0.89Fe2+0.06Fe3+0.03Ti0.02)[Si1.94Al0.06O6]
wollastonite Ca0.99Ca0.99Ca0.99[Si3.01O9]
xonotlite
phlogopite
phlogopite

 



hibonite in thin section

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hibonite grossular vesuvianite in thin section

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sample: FKM-263 (dealer sample number 3740; two thin sections cut from the same billet are shown here; the analyses presented in the composition table are from the lower pictured thin section).
locality: Tashelga River, Gornaya Shoria region, Kemerovskaya Oblast’, Russia.
rock type: “calc-skarnoid”. Geology is described in Konovalenko et al., 2012.
major mineralogy: specimen acquired for hibonite. This sample is from the same general vicinity of sample FKM-270 and is very similar in mineralogy.
accompanying videos: Short videos featuring the mineral associations and optical properties of the hercynite, hibonite and vesuvianite in this thin section offer a more detailed look at this sample.

mineral representative mineral compositions in FKM-263
corundum (Al1.99Fe3+0.01)O3
magnetite (Fe2+0.98Mg0.01Ca0.01)(Fe3+1.98Al0.02)O4
hercynite (Fe2+0.54Mg0.44Mn2+0.02)(Al1.92Fe3+0.08)O4
hibonite (Ca0.98Ce0.01Sr0.01Na0.01)(Al10.27Ti0.54Fe3+0.50Fe2+0.34Mg0.26Si0.07Mn2+0.01)O19
tashelgite (Ca1.97Na0.03)(Mg1.83Mn2+0.07Fe2+0.05Fe3+0.02Zn0.01)Fe2+2.00(Al0.73Fe3+0.27)[Al2.00O][Al1.00(OH)][Al14.00O31(OH)]
calcite Ca1.00[CO3]
fluorapatite Ca4.99[P0.93Si0.037S0.03O4]3(F0.70[OH]0.25Cl0.05)
monazite-(Ce) (Ce0.44La0.23Nd0.13Pr0.04[HREE]0.03Ca0.03Sm0.02Y0.02Gd0.01)[P0.99Si0.01O4]
grossular (core) (Ca2.90Fe2+0.08Mn2+0.01Mg0.01)(Al1.53Fe3+0.36Ti0.09Zr0.02)[Si0.95Al0.050.003O3.987F0.013]3
grossular (rim) (Ca2.90Fe2+0.07Mn2+0.01Mg0.01)(Al1.58Fe3+0.34Ti0.07Zr0.01)[Si0.96Al0.0370.003O3.987F0.013]3
vesuvianite (core) (Ca18.57Fe2+0.38Mn2+0.02Ce0.01Y0.01)(Al0.77Ti0.23)OAl10.00(Fe2+0.82Mg0.71Fe3+0.27Ti0.18V0.01)□5.00
[Si1.98Al0.02O7]4[Si1.00O4]10([OH]7.73F1.25Cl0.01)
vesuvianite (rim) (Ca18.56Fe2+0.39Mn2+0.01Sr0.01Y0.01Nd0.01)(Ti0.90Fe3+0.10)OAl10.00(Fe2+1.05Mg0.900.05)□5.00
[Si1.95Al0.05O7]4[Si1.00O4]10([OH]7.62F1.12Cl0.26)

 



magnesio-hastingsite in thin section

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sample: FKM-264 (dealer sample number 3556)
locality: Kovdor massif, Russia.
rock type: “amphibole-calcite rock”. This sample, as well as similar sample FKM-265 (also from the Kovdor massif), is somewhat enigmatic because as an isolated small billet-sized specimen, there is no geologic context to establish its field relationships relative to other local rocks. Hence, it is petrologically ambiguous whether the sample should be considered igneous and directly related to the carbonatite or associated alkaline mafic/ultramafic magmas, or whether the sample is of metasomatic origin and so related instead to hydrothermal alteration accompanying the intrusive event. Chakhmouradian & Zaitsev, 1999 and Chakhmouradian & Zaitsev, 2002 describe mineralogically similar rocks from the nearby and geologically comparable Afrikanda complex, and attribute them to crystallization of a “silicocarbonatite” magma that has intruded earlier ultramafic rocks. Earlier Russian work (references in Chakhmouradian & Zaitsev, 1999; 2002) alternatively suggest that the clinopyroxene-amphibole-calcite rocks from several of the Kola carbonatite-affiliated localities may result from the metasomatic interaction between a CO2-rich “fluid”(melt?) and ultramafic melilitic host rocks (for example, a rock perhaps akin to FKM-262).
major mineralogy: The sample consists of essentially only calcite and weakly-zoned magnesio-hastingsite. Very minor OH-rich apatite and minor zoned Na-enriched phlogopite are also present.
accompanying videos: Short videos featuring the mineral associations and optical properties of the magnesio-hastingsite in this thin section offer a more detailed look at this sample.

mineral representative mineral compositions in FKM-264
calcite (Ca0.99Sr0.01)[CO3]
hydroxylapatite (Ca4.92Ce0.02La0.01Nd0.01Sr0.01Th0.01Fe2+0.01)[P0.97Si0.03O4]3([OH]0.66F0.34)
magnesio-hastingsite
(most [Si+Mg]-rich)
(Na0.79K0.120.09)(Ca1.90Na0.10)(Mg3.72Fe3+0.66Al0.31Fe2+0.26Ti0.02Mn2+0.02)
[Si6.20Al1.80O22]([OH]1.94O0.04F0.02)
magnesio-hastingsite
(most Al-rich)
(Na0.80K0.11Sr0.010.08)(Ca1.92Na0.08)(Mg3.69Fe3+0.84Al0.30Fe2+0.11Ti0.03Mn2+0.02)
[Si6.00Al1.99O22]([OH]1.93O0.06F0.01)
magnesio-hastingsite
(most Ca-rich)
(Na0.88K0.11Sr0.01)(Ca1.97Na0.03)(Mg3.65Fe3+0.58Fe2+0.39Al0.32Ti0.03Mn2+0.02)
[Si6.11Al1.89O22]([OH]1.92O0.06F0.02)
phlogopite (high z core
of relict “seed” interior)
(K0.53Na0.38Ba0.070.02)(Mg2.47FeT0.33Al0.18MnT0.01Ti0.01)[Si2.68Al1.32O10]([OH]1.98O0.01)
phlogopite (low z tip
of relict “seed” interior)
(K0.61Na0.30Ba0.020.07)(Mg2.60FeT0.28Al0.11MnT0.01Ti0.01)[Si2.83Al1.17O10]([OH]1.98O0.02)
phlogopite (outer rim of
host crystal)
(K0.60Na0.30Ba0.060.04)(Mg2.63FeT0.27Al0.07MnT0.01Ti0.01)[Si2.79Al1.21O10]([OH]1.98O0.01F0.01)
phlogopite (weakly higher
z inner band of host crystal)
(K0.83Na0.10Ba0.04Ca0.010.02)(Mg2.68FeT0.32)[Si2.85Al1.14Fe3+0.02O10](OH)2.00
phlogopite (weakly lower
z core of host crystal)
(K0.60Na0.30Ba0.040.06)(Mg2.64FeT0.28Al0.06Ti0.01)[Si2.80Al1.20O10]([OH]1.99O0.01)

 



katophorite in thin section

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sample: FKM-265 (dealer sample number 2475)
locality: Kovdor massif, Russia.
rock type: “clinopyroxene-amphibole-calcite rock”. This sample, as well as similar sample FKM-264 (also from the Kovdor massif), is somewhat enigmatic because as an isolated small billet-sized specimen, there is no geologic context to establish its field relationships relative to other local rocks. Hence, it is petrologically ambiguous whether the sample should be considered igneous and directly related to the carbonatite or associated alkaline mafic/ultramafic magmas, or whether the sample is of metasomatic origin and so related instead to hydrothermal alteration accompanying the intrusive event. Chakhmouradian & Zaitsev, 1999 and Chakhmouradian & Zaitsev, 2002 describe mineralogically similar rocks from the nearby and geologically comparable Afrikanda complex, and attribute them to crystallization of a “silicocarbonatite” magma that has intruded earlier ultramafic rocks. Earlier Russian work (references in Chakhmouradian & Zaitsev, 1999; 2002) alternatively suggest that the clinopyroxene-amphibole-calcite rocks from several of the Kola carbonatite-affiliated localities may result from the metasomatic interaction between a CO2-rich “fluid”(melt?) and ultramafic melilitic host rocks (for example, a rock perhaps akin to FKM-262).
major mineralogy: The specimen was acquired for “magnesio-katophorite” (note that the katophorite-root amphiboles have been re-defined to give rootname precedence to the Mg+Al-dominant end-members, so the “magnesio-” prefix is no longer used in this case). However, no katophorite was observed; the amphibole in the sample is actually weakly-zoned magnesio-hastingsite. Accompanying the amphibole are abundant calcite and weakly-zoned diopside. Minor accessory minerals include magnetite (zoned in Cr) and perovskite, sparse hydroxylapatite, and sparse intergrown pyrrhotite and pentlandite. A single [Ti+Cr]-enriched garnet (apparently “hydro-andradite”) occurs as an inclusion in the amphibole.
accompanying videos: Short videos featuring the mineral associations and optical properties of the diopside and magnesio-hastingsite in this thin section offer a more detailed look at this sample.

mineral representative mineral compositions in FKM-265
pyrrhotite (Fe0.92Ni0.01)S1.00
pentlandite (Ni4.61Fe4.10Co0.28)S8.01
magnetite (most Cr-rich) (Fe2+0.92Mg0.04Mn2+0.03Zn0.01)(Fe3+1.57Cr0.31Fe2+0.05Ti0.05Al0.02)O4
magnetite (most Fe-rich) (Fe2+0.94Mn2+0.03Mg0.02Zn0.01)(Fe3+1.79Cr0.10Fe2+0.05Ti0.05Al0.01)O4
perovskite (Ca0.96Na0.03Sr0.01)(Ti0.99Fe3+0.01)O3
calcite Ca1.00[CO3]
hydroxylapatite (Ca4.90Sr0.03Na0.03Fe2+0.01Ce0.01Y0.01)[P0.99Si0.01O4]3([OH]0.68F0.32)
“hydro-andradite” (Ca2.87Fe2+0.11Mn2+0.01Na0.01)(Fe3+1.07Ti0.33Fe2+0.24Al0.18Cr0.10Mg0.08Zr0.01)[Si0.9030.097O3.617(OH)0.383]3
diopside (most [Na+Fe]-rich) (Ca0.92Na0.08)(Mg0.76Fe2+0.15Fe3+0.08Cr0.01)[Si1.99Al0.01O6]
diopside (most [Ca+Mg]-rich) (Ca0.99Na0.01)(Mg0.91Fe2+0.07Fe3+0.02)[Si1.98Al0.01O6]
magnesio-hastingsite
(most Al-rich)
(Na0.83K0.110.06)(Ca1.88Na0.12)(Mg3.47Fe3+0.70Fe2+0.51Al0.24Ti0.04Cr0.02Mn2+0.01Ni0.01)
[Si6.20Al1.80O22]([OH]1.91O0.08F0.01)
magnesio-hastingsite
(most Mg-rich)
(Na0.93K0.07Sr0.01)(Ca1.94Na0.07)(Mg3.86Fe3+0.61Fe2+0.31Al0.15Ti0.05Mn2+0.01)
[Si6.27Al1.73O22]([OH]1.87O0.10F0.03)
magnesio-hastingsite
(most Si-rich)
(Na0.89K0.070.04)(Ca1.88Na0.12)(Mg3.53Fe2+0.62Fe3+0.58Al0.16Ti0.07Mn2+0.02Cr0.01)
[Si6.40Al1.60O22]([OH]1.85O0.14F0.01)

 



pyrope bronzite and diopside in thin section

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sample: FKM-266
locality: Gusdal Olivine Pit (Åheim Olivine Pit), Almklovdalen, Vanylven, Møre og Romsdal, Norway.
rock type: amphibolized garnet websterite; although pods of mineralogically similar eclogite (garnet+clinopyroxene) also occur at the locality, the clinopyroxene of the eclogite is omphacite, whereas the clinopyroxene of the websterite is diopside. A detailed structural and petrologic evaluation of the area is given in Seljebotn, 2016.
major mineralogy: specimen acquired for pyrope.
accompanying videos: Short videos featuring the mineral associations and optical properties of the pyrope in this thin section offer a more detailed look at this sample.

mineral representative mineral compositions in FKM-266
pyrrhotite (troilite?) Fe1.01S1.00
pentlandite (Ni4.75Fe4.16Co0.14)(S7.93As0.01)
rutile (Ti0.99Cr0.01)O2
pyrope (Mg1.90Fe2+0.69Ca0.38Mn2+0.03)(Al1.98Fe3+0.01Cr0.01)[Si0.997Al0.003O4]3
enstatite Mg0.99(Mg0.81Fe2+0.17Fe3+0.02)[Si1.98Al0.02O6]
diopside (Ca0.88Na0.09Mg0.03)(Mg0.86Al0.07Fe2+0.04Fe3+0.02)[Si1.98Al0.01O6]
magnesio-hornblende (Na0.41K0.03Sr0.010.55)(Ca1.65Na0.35)(Mg4.02Al0.47Fe3+0.42Ti0.04Cr0.03Mn3+0.01Ni0.01)
[Si6.60Al1.40O22]([OH]1.90O0.09Cl0.02)

 



piemontite in thin section

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sample: FKM-267 (dealer sample number 3585)
locality: ~50 km NW of Petropavlovsk-Kamchatsky, Kamchatka, Russia. The specific locality may be in the vicinity of the villages of Koryaki(?) or Razdol’nyy(?), both of which are in the correct direction and at the approximate distance from Petropavlovsk-Kamchatsky. Both are also along a major road (R474), so perhaps easier accessibility for mineral collecting in the adjacent hills?
rock type: test.
major mineralogy: specimen acquired for piemontite.

 



fluor-dravite and corundum in thin section

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sample: FKM-268
locality: Hazrat Saeed, Koksha Valley, Khash & Kuran Wa Munjan Districts, Badakhshan Province, Afghanistan.
rock type: although originally thought to be a simple pegmatite- or greisen-related assemblage of relatively Fe-rich “fluor”-tourmaline and muscovite, the unexpectedly high Mg content of the tourmaline (almost Fe-free oxy-dravite) and the mica (phlogopite rather than muscovite) indicate a less clear origin. Like some of the other samples featured here with B or Be minerals in a phlogopite±clinochlore matrix, it’s possible the sample represents more of a “blackwall”-style alteration assemblage of granite-related B-rich fluids pervasively infiltrating more mafic (Mg-bearing) adjacent host rocks (for example, see the chrysoberyl and Mg-rich phyllosilicate assemblage in sample FKM-156). Alternatively, the sample might instead represent a larger scale Mg-metasomatism event rather than a more localized granite-related B-metasomatism event? Work by Dutrow et al., 2019 [← subscription required] proposes the assemblage represents a metacarbonate protolith modified by subsequent [B+Mg+K]-metasomatism. Regardless of whether the sample is the product of localized or more widespread metasomatism, however, the rock would still be best described as a corundum-[Mg-tourmaline]-phlogopite metasomatite.
major mineralogy: The hand sample consists of large deep-inky-blue tourmaline crystals in a pale-colored coarse-grained mica matrix, with scattered tiny blue sapphires, and the specimen was specifically acquired for fluor-dravite (noted on the dealer label) and muscovite (presumed from the high alumina assemblage). However, analyses of the tourmaline indicate that the large prophyroblasts are essentially an unzoned low-F oxy-dravite composition that plots near the nomenclature “corner” boundary with adjacent dravite, uvite and oxy-uvite; indeed, a weak compositional gradation near the rim corresponds to uvite. For a limiting M3+/∑M = 0 (M = Fe+Mn), calculated W[O/(O+OH+F)] ≈ 0.65 for the oxy-dravite core; hence, a dravite composition would be increasingly precluded with increased M3+/∑M. For the thin presumed uvite composition band near the rim, calculated W[O/(O+OH+F)] of course also increases with increasing M3+/∑M; however, in contrast to the wholly nomenclature-bounded oxy-dravite core, the rim calculated W[O/(O+OH+F)] composition would cross the uvite/oxy-uvite nomenclature boundary at a value of M3+/∑M > 0.39. In addition to the presumed tourmaline not being fluor-dravite, the presumed mica is also not muscovite, but rather a very Mg-rich phlogopite. The phlogopite shows some incipient alteration along cleavage planes to a similarly very Mg-dominant clinochlore, although scattered coarser clinochlore is also present. One small mass of an Fe-rich chlorite intimately admixed with fine-grained Fe-oxide was observed (as was a separate too-small-to-quantitatively-analyze Fe-oxide [or Fe-oxyhydroxide] in the phlogopite). The presumed sapphire (also blue cathodoluminescence) is indeed corundum, with ~1100 ppm Fe and ~190 ppm Ti. A cluster of elongated dolomite crystals are present in one portion of the sample. Scattered tiny zircon are widespread in the mica; one slightly larger crystal contained a small uraninite inclusion.

mineral representative mineral compositions in FKM-268
corundum Al2.00O3
uraninite (inclusions in zircon) not analyzed
dolomite Ca1.00(Mg0.95Fe2+0.05Mn2+0.01)[CO3]2
zircon not analyzed
dravite (intergrown with corundum) (Na0.64Ca0.170.19)(Mg2.59Al0.31Fe2+0.10)Al5.93
[Si6.07O18](BO3)3(OH)3([OH]0.60O0.38F0.02)
oxy-dravite-dominant tourmaline ss
(core of large crystals)
(Na0.48Ca0.470.05)(Mg2.54Al0.35Fe2+0.11)Al6.00
[Si5.92Al0.08O18](BO3)3(OH)3(O0.65[OH]0.21F0.13)
uvite-dominant tourmaline ss
(rim of large crystals)
(Ca0.51Na0.45Sr0.010.03)(Mg2.75Fe2+0.24)(Al5.77Mg0.16)
[Si6.08O18](BO3)3(OH)3(O0.41[OH]0.39F0.20)
phlogopite (K0.87Na0.040.09)(Mg2.54Al0.31FeT0.140.01)[Si2.77Al1.23O10]([OH]1.92F0.07Cl0.01)
clinochlore (Mg4.23Al1.28FeT0.340.15)[Si2.94Al1.06O10]([OH]7.96F0.03O0.01)
“mixed [Fe-Mg-Al]-chlorite” (K0.01Na0.01Ca0.01)(FeT2.08Al1.78Mg1.640.50)[Si2.94Al1.06O10]([OH]7.96Cl0.03F0.01)

 



pumpellyite-(Mn2+) in thin section

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sample: FKM-269 (dealer sample number 734)
locality: Bikkulovskoe deposit, Southern Urals, Urals Region, Russia.
rock type: test.
major mineralogy: specimen acquired for pumpellyite-(Mn2+), piemontite, andradite and caryopilite.

 



tashelgite and hibonite in thin section

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sample: FKM-270 (dealer sample number 4571)
locality: Tashelga River, Gornaya Shoria region, Kemerovskaya Oblast’, Russia.
rock type: “calc-skarnoid”. Geology is described in Konovalenko et al., 2012.
major mineralogy: specimen acquired for tashelgite. This sample is from the general vicinity of sample FKM-263.

 



nagelschmidtite in thin section

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sample: FKM-271 (dealer sample number 4633)
locality: Hatrurim Formation, Negev, Israel. The Hatrurim Formation outcrops in numerous localities in Israel, from near the Syrian border in the north to near the town of Arad in the northern Negev desert area in the south of the country (Gross, 2016); additional outcrops also occur in the Palestinian West Bank and in Jordan. Unfortunately, the dealer’s label did not specify a more detailed locality beyond “Negev”, so the large outcrop of the Hatrurim near Arad is thought to be the most likely source of this material.
rock type: The rock is an apatite-kalsilite-wollastonite-andradite-gehlenite potassic-phosphatic metacarbonate paralava (or slag). More generally, it is a sanidinite facies pyrometamorphic paralava rich in K (as kalsilite), P (as apatite and various phosphosilicates), and several high-temperature Ti- and Fe3+-rich calcium silicates. The UHT mineral assemblage was formed by the combustion of contained bitumens in the rock, and possibly also accompanied by some additional auto-metasomatism. A plausible original sedimentary protolith for this rock may have been an organic-rich [supplying the combustable material] glauconitic [supplying the K and Fe] limestone or marl [supplying the Ca], presumably with associated apatite and possibly also with some associated dolomite or gypsum/anhydrite/barite. Interestingly, rankinite and larnite, typically common and widespread in the local assemblages, were not observed in this particular sample.
major mineralogy: The specimen was acquired for nagelschmidtite. Although a calcium phospho-silicate superficially resembling nagelschmidtite occurs as inclusions in Ti-rich andradite (see plate XXVI-f in Gross, 2016 [reproduced from Seryotkin et al., 2012]) and in gehlenite, the composition appears to better correspond to the related mineral flamite. Gfeller et al., 2015 provide flamite composition data from several assemblages, and the major element chemistry of the dominant calcium phospho-silicate in this samples quite closely matches the average of the flamite in the “eutectic intergrowth with gehlenite” assemblage of their paralava sample (table 2, column 2); some of the minor elements are however somewhat more enriched and actually more closely match those of their column 1 “rankinite-hosted” flamite analyses. In any case, however, if flamite is approximated by the composition Ca7.50.5[SiO4]3[PO4] and nagelschmidtite is approximated by the composition Ca7□[SiO4]2[PO4]2, then the dominant inclusions in this sample, in both garnet and andradite, would appear to be flamite. In addition to the presumed flamite, two additional calcium phospho-silicates were also observed, one so far only as a single inclusion in garnet, and the other so far only as single inclusion in melilite. These two phospho-silicates have proven rather enigmatic to characterize, as neither appears to correspond to familiar minerals. Unlike flamite and compositionally similar minerals such as nagelschmidtite and silicocarnotite, each of which should total to ~100 wt%, these unidentified phases total to only ~85 wt% and indicate missing light element components (likely OH and/or H2O, but potentially CO3 or even BO3). After considerable testing with different normalization schemes, the lone inclusion in garnet appears to be most consistent with a [P+S]-substituted afwillite, with a predicted end-member formula of (Ca8□)[PO4]3[Si3O7(OH)5] . 6H2O; compare this to afwillite proper: (Ca8Ca)[SiO4]3[Si3O6(OH)6] . 6H2O. In addition to the measured chemistry, calculated charge balance and ~100 wt% analytical total (with water from OH and H2O included) conforming reasonably well to an afwillite-type stoichiometry, another supportive feature of the normalization is that the afwillite structure includes isolated silicate tetrahedra; presumably it is easier to replace these isolated SiO4 groups with similar isolated PO4 or even SO4 groups than it would be to substitute P or S into more polymerized silicate groupings. The second calcium phospho-silicate phase, the lone inclusion in melilite, has been even more problematic to normalize. Presuming ∑T=6, Si normalizes nicely to 3.99 apfu and P (including additional minor S and V) normalizes to 2.01 apfu, but Ca normalizes to only 6.5 apfu and the required negative charge required to balance the cations is an unusual -38.998 (hence -39). This value could correspond to O19(OH), O18(OH)3, or similar increasingly hydrous variants [or alternatively, something more exotic akin to O18(BO3)]. In any case, the low overall (-) charge precludes the simpler isolated tetrahedra model ascribed to the other unknown inclusion, and requires a more polymerized model. This unfortunately makes narrowing down the most likely structural assignment much more difficult. Similarly, the potential variability in OH (if OH is present) cannot be estimated from the missing analytical total, as the difference could just be accommodated by more or less H2O. Ultimately, the ∑T=6 normalization model seems compelling (although ∑T=3 or ∑T=12 or other such multiples work just as well), even if a structural assignment can’t be made. An empirical formula based on that normalization, and assuming 3[OH] and 6H2O, is the one presented here. Clearly both poorly-characterized calcium phospho-silicate minerals (particularly the latter), would benefit from further study and additional analytical spots, if additional grains are found.
accompanying videos: Short videos featuring the mineral associations and optical properties of the andradite, gehlenite, wollastonite and kalsilite in this thin section offer a more detailed look at this sample.

mineral representative mineral compositions in FKM-271
hematite
magnetite
barite
apatite
apatite
andradite (most Ti-rich) Ca2.99(Fe3+1.29Ti0.68V0.01Mg0.01)[Si0.76Fe3+0.15Al0.09P0.003O4]3
andradite (most [Si+Fe3+]-rich) Ca2.99(Fe3+1.45Ti0.53V0.02Mg0.01)[Si0.817Fe3+0.107Al0.073P0.003O4]3
flamite (in melilite; most K-rich) (Ca6.68K0.53Na0.51Ba0.07Sr0.05Mg0.05Mn2+0.01Cu0.010.09)[Si0.708P0.278Fe3+0.005V5+0.005S0.003O4]4
flamite (in garnet; most Na-rich) (Ca6.71Na0.73K0.22Sr0.04Ba0.01Cu0.010.08)[Si0.708P0.28Fe3+0.005Al0.003V5+0.003S0.003O4]4
“[P+S]-substituted afwillite”?
(Ca8□)[PO4]3[SiO3(OH)][SiO2(OH)2]2 . 6H2O
(alternative OH configurations possible)
(Ca7.90Fe2+0.04K0.02Na0.02Cu0.02Sr0.010.99)[P0.717S0.22Al0.05V5+0.02O4]3
[Si0.99O3([OH]0.98F0.01Cl0.01)][Si1.00O2(OH)2]2 . 6H2O
unknown possible P-substituted
calcium silicate hydrate (C-S-H)?
(Ca6.43Fe2+0.07Sr0.02La0.01?)[P0.925S0.06V5+0.02O4]2
[Si3.99?O10([OH]2.79Cl0.16F0.05)] . ~5-6H2O
“Fe-åkermanite”? (inclusion in
apatite inclusion in garnet)
(Ca1.97K0.02)(Fe2+0.81Fe3+0.16Ti0.02V0.01)[Si1.78Al0.16Fe3+0.05P0.01O7]
melilite (weakly lower z) (Ca1.86Na0.12K0.02)(Al0.49Fe3+0.34Mg0.15Zn0.01)[Si1.30Al0.70O7]
melilite (main weakly higher z) (Ca1.72Na0.22K0.03Sr0.03Ba0.01)(Al0.32Fe3+0.30Mg0.27Fe2+0.04Cu2+0.02Zn0.01Mn2+0.01Ni0.01)[Si1.63Al0.37O7]
wollastonite/
parawollastonite?
kalsilite
“zeolite”
cebollite

 



pecoraite in thin section

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sample: FKM-272 (dealer sample number 3074)
locality: Ufalei Ni deposit, Ufaley District, Chelyabinsk Oblast’, Southern Urals, Russia.
rock type: test.
major mineralogy: specimen acquired for pecoraite.

 



trolleite rutile and kyanite in thin section

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sample: FKM-273 (dealer sample number 3659)
locality: Hålsjöberg, Torsby, Värmland, Sweden.
rock type: test.
major mineralogy: specimen acquired for trolleite.
accompanying videos: Short videos featuring the mineral associations and optical properties of the rutile, berlinite, scorzalite, trolleite, burangaite and kyanite in this thin section offer a more detailed look at this sample.

mineral representative mineral compositions in FKM-273
hematite
rutile (Ti0.99Fe3+0.01)O2
berlinite Al1.00P1.00O4
fairfieldite group
bederite (wicksite)
variscite/metavariscite
scorzalite (most Fe3+-rich) (Fe2+0.75Fe3+0.15Mg0.02Mn2+0.01)(Al1.64Fe3+0.36)[P1.00O4]2(OH)2.00
scorzalite (most Al-rich) (Fe2+0.91Mg0.06Mn2+0.03)(Al1.98Ti0.02)[P1.00O4]2(OH)2.00
trolleite
crandallite
(main; most Ca-rich)
crandallite
(patchy; most Sr-rich)
burangaite
kyanite (Al1.98Fe3+0.02)O1.00[Si0.99Al0.01O4]

 



wodginite and Rb-muscovite in thin section

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sample: FKM-274 (dealer sample number 4004)
locality: Vishnyakovskoe Rb-Ta deposit, Irkutskaya Oblast’, Prebaikalia, Eastern-Siberian Region, Russia.
rock type: well-differentiated Cs-Rb-Ta-Sn granitic pegmatite.
major mineralogy: specimen acquired for wodginite, Rb-bearing muscovite and alkali feldspar (also Rb-bearing?). An essentially identical-appearing specimen from Pavel Kartashov’s collection (minID: UM7-UQF) is described as containing rubidian muscovite with up to 2.7 wt% Rb2O, spherulitic aggregates of wodginite rimmed by ixiolite, and albite.

 



miserite and aegirine in thin section

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sample: FKM-275
locality: Union Carbide Mine, Wilson Springs (Potash Sulfur Springs), Garland Co., Arkansas, USA.
rock type: test.
major mineralogy: specimen acquired for miserite.

 



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