samples FKM-201 to FKM-225


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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sample: FKM-201
locality: Schmorrasgrat-Süd, Starlera, Ferrera Valley, Grischun, Switzerland.
rock type: add rock type.
major mineralogy: Calderite was reported for this sample, but all of the garnet examined in this thin section was verified by EPMA as Mn-rich andradite (however, with a significant calderite component). In addition to garnet, aggregates of Mn-enriched aegirine-augite admixed with a calcite-rhodochrosite solid-solution carbonate are present. Several large patchy-zoned barite crystals are also present, and thin irregular discontinuous veinlets of hematite are abundant in the garnet.
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-201
hematite (Fe3+1.99Mn3+0.01)O3
calcite (Ca0.63Mn2+0.35Mg0.02)[CO3]
barite (most Sr-rich) (Ba0.94Sr0.04Na0.01)[S1.00O4]
barite (main) (Ba0.97Sr0.02Na0.01)[S1.00O4]
andradite (Ca1.83Mn2+1.16Mg0.01)(Fe3+1.82Al0.12Mn3+0.05)[Si2.99O12]
aegirine-augite (Na0.75Ca0.23Mn2+0.02)(Fe3+0.71Mn2+0.15Mg0.10Al0.02Mn3+0.01)[Si2.00O6]


sample: FKM-202
locality: “hibonite locality”, Sierra de Comechingones, San Luis province, Argentina.
rock type: This rock is purportedly from a natural occurrence, but it bears a strong resemblance to an artificial smelter by-product, and is questioned as such in the mindat locality description. However, the overall sample texture, the lack of silicates that would normally be expected to be encountered in conventional vanadium-refining slag, and the somewhat atypical low-Fe composition of the vanadium present in the sample all suggest that if this actually is a smelter product, it’s not necessarily an ordinary commercial one (i.e. one that is the by-product of the routine production of ferro-vanadium). Alternatively, it is perhaps possible that this sample represents a lab-grown material (e.g. the by-product of a thermite reaction to produce vanadium), as such an origin would allow for much more flexibility with regard to both texture (i.e. control of the cooling rate) and the bulk composition. As for the possibility that this is from a natural occurrence, I wouldn’t want to rule that out based only on this one sample. However, I remain extremely skeptical. Although high-grade metamorphism is described from the area from which this sample is reported (but almost certainly not as “ultra”-UHT as this material would seem to require… droplets of what was once molten vanadium are present!), I’m hard-pressed to imagine a natural protolith with this bulk composition that can also end up so strongly reduced. Given the unusual and perhaps even unique nature of this material if it is indeed natural, I would definitely like to see the original collectors publish a detailed geologic description of the occurrence in the peer-reviewed literature.
major mineralogy: This sample is enigmatic and bears no petrologic similarity to the well-known hibonite-bearing rocks of Madagascar (for example, see sample FKM-191); indeed, this sample bears little resemblance to any typical terrestrial rock. Unlike the silicate- and carbonate-rich bulk mineralogy of the Madagascar hibonite occurrences, this purported Argentinian material is essentially silicate-free and is composed almost entirely of Al-rich oxide minerals. The dominant phase is coarse blocky grossite (dark and lustrous in hand sample). Hosted in the grossite with an ophitic to sub-ophitic texture are abundant coarse laths of one or possibly two additional aluminum-rich oxide phases containing variable proportions of K, Na, Mg and V (reminiscent of diaoyudaoite, and both the K-dominant and Na-dominant compositions are here considered as and normalized as such), as well as abundant hibonite (see BSE images of FKM-202 for a closer look at the mineralogy and textures). The hibonite occurs both as discrete crystals within the grossite and as an intimate intergrowth with the alkali-rich oxide phase(s). In fact, in some cases, it appears as if single crystals compositionally grade between Ca-rich (hibonite) and the alkali-rich zones. The hibonite, nominally U(-), is here instead B(-) with a 2V° < 10°, suggesting either sample strain or an unexpected compositional ordering. Also, unlike that of the Madagascar occurrences, this hibonite is REE-free. Perhaps the most unusual feature of this rock (and the strongest suggestion of a possible slag origin) are the large droplets and finer-scaled arborescent growths of “native” vanadium that are abundantly scattered in the grossite. A closer examination of the droplets shows that in some cases they are multi-phasic, with a low-Fe vanadium central subhedral crystal (with ~1.5 wt% Fe) surrounded by a dendritic growth of a higher-Fe vanadium (with ~6.3 wt% Fe). In addition to the aforementioned minerals, another abundant phase (referred to here as “Al-V-Mg-oxide”) contains major V, Al, Mg and presumably oxygen, along with small amounts of Ti, Ca and Mn. The analysis of this material by EPMA has been challenging and it remains inadequately characterized. WDS scans using TAP, PET, LIF and PC2 crystals show that from carbon onwards, no major elements besides those listed are present (i.e. the material is not a carbide or nitride; H, Li, Be and B can not be ruled out but would seem unexpected). The evidence for oxygen is somewhat ambiguous due to the unfortunate significant overlap of the O Kα X-ray line with the V Lβ and V Lα lines; however, oxygen is believed to be present (and also, if the material is treated as an oxygen-free metal alloy, then the analytical total comes in low at only 67 wt%). However, if the phase is an oxide, there is still some question as to the appropriate valences of the metals. If V and Ti in this material are assigned their typical “reduced” terrestrial valences of V3+ and Ti4+, then the analytical oxide total comes in high at ~108-110% wt% (note that oxygen isn’t directly measured here due to the X-ray interference, but is instead calculated by charge balance). This suggests that these metals could be even more reduced. Hence, to optimize the analytical total and the overall charge balance, the phase is best approximated as containing V2+ and Ti2+, with oxygen treated as slightly non-stoichiometric. Given the reduced nature of the sample, there is some justification in assigning an atypical +2 valence to V and Ti (although the presence of perovskite with Ti4+ complicates the divalent cation hypothesis). In any case, this phase would certainly benefit from additional study. As noted earlier, the entire rock is essentially Si-free. However, there are in places cavities between the larger grossite crystals that are filled with clusters of gehlenite intergrown with perovskite, fluorite and sometimes minor calcite. Overall, whether natural or artificial, this sample has been a fascinating specimen to examine under the microscope and with the microprobe, and the unusual composition has allowed me to better appreciate some of the challenges of analyzing atypical materials. If natural, several of these phases may be new minerals or new geologic occurrences of existing minerals, and warrant further scientific study.
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-202
grossite (Ca0.99Na0.01)(Al3.98Si0.01V0.01)O7
perovskite (Ca0.99Na0.01)(Ti0.84Al0.11Zr0.03Si0.02V0.01)O3
hibonite Ca0.99(Al11.33V0.52Mg0.11Ti0.04Si0.01)O19
“K-diaoyudaoite” (?) (K0.46Na0.18Ca0.010.35)(Al10.06Mg0.57VT0.35MnT0.01TiT0.01)O17
diaoyudaoite (?) (Na0.73K0.49)(Al9.99Mg0.59VT0.38MnT0.02TiT0.01Si0.01)O17
“Al-V-Mg-oxide” (?) Ca0.04(Al5.84VT3.04Mg1.94TiT0.10CrT0.05MnT0.04)O13.92 (?)
gehlenite (Ca1.87Na0.11)(Al0.96Mg0.04V0.02)[Si1.09Al0.91O7]


sample: FKM-203
locality: Sannidal, Kragerø, Telemark, Norway.
rock type: apatite-chlorite-actinolite metasomatite. This rock appears to be an albite-epidote hornfels to greenschist facies metasomatized equivalent of some originally Mg-rich protolith (possibly a previously-altered basalt, volcanoclastic rock or graywacke). The notable Cl and REE enrichments suggest alkali-chloride metasomatism (akin to the alteration associated with “iron-apatite” [IOCG] mineralization; see for example sample FKM-44, a more Ca-dominant analog of this more Mg-rich rock). Metasomatism may be related to the remobiliztion of early-formed late Carboniferous evaporites by later magma-driven seawater circulation accompanying the opening of the Oslo Rift in the Permian (postulated from the general rifting history, e.g. see Larsen et al., 2008).
major mineralogy: Relict actinolite partially altered to clinochlore and quartz. Abundant large Cl-bearing hydroxylapatite heavily included with small monazite are present. Scattered small xenotime and scattered larger complexly-zoned allanite-(Ce) occur both in the apatite and in the chlorite. Minor tiny TiO2 (rutile?) is also present.
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-203
monazite-(Ce) (Ce0.47La0.21Nd0.18Pr0.05Ca0.03Sm0.02Gd0.02[HREE]0.02Y0.02)[P0.99O4]
hydroxylapatite (Ca4.97Ce0.01Na0.01)[P2.99O12]([OH]0.68Cl0.19F0.13)
(low z zone)
(mod-low z zone)
(mod-high z zone)
(high z zone)
actinolite (K0.030.97)(Ca1.70Na0.18Fe2+0.11Mn2+0.01)(Mg3.81Fe2+0.70Fe3+0.38Al0.06Ti0.04V0.01)
clinochlore Ca0.03(Mg3.37FeT1.23Al1.08MnT0.010.31)[Si3.15Al0.85O10](OH)8.00


sample: FKM-204
locality: unspecified locality from the Grenville geologic province, Québec, Canada.
rock type: scapolite marble.
major mineralogy: specimen acquired for meionite. Based on petrography, meionite and calcite are present. The measured Br content of the scapolite is 17±4 ppm (1σ; n=3) and molar Cl/Br = 691. Br was measured by EPMA by counting Br Kα X-rays on five spectrometers simultaneously (using two LIF and three LLIF crystals) at 25 kV and 500 nA for 240 seconds on-peak. To minimize sample damage under these extreme conditions, the beam was slightly defocused to 5 μm and also slowly moved across the sample. The 1σ detection limit under these conditions is roughly 9 ppm Br.
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-204
meionite (Ca1.70Na1.19K0.10Sr0.01Mg0.01)[Si7.25Al4.74O24] . (Ca0.87Na0.07)([CO3]0.69[SO4]0.15Cl0.13)


sample: FKM-205
locality: Anosy region, Tuléar province, Malagasy Republic.
rock type: thorianite-spinel-pargasite-diopside marble. Granulite facies metacarbonate.
major mineralogy: Predominately a calcite marble with abundant porphyroblasts of Al-rich diopside (also with up to 2220 ppm Zr), with subordinate porphyroblasts of K-rich fluoro-pargasite (also with up to 1140 ppm Zr) and spinel. Some of the amphibole is enclosed within cpx and suggests an incomplete prograde amphibole-out reaction. In other areas, clots of what appears to be either an unusual VIAl-rich serpentine or a similarly unusual IVAl-free chlorite enclose relict amphibole, and these clots are then curiously rimmed by a relatively unzoned thin band of dissakisite-(Ce), which also occurs as scattered small discrete grains (the grains are irregularly zoned) and as scattered thin discontinuous veinlets elsewhere in the sample. Several coarse veinlets of a low z Ca-Na-aluminosilicate (86-89 wt% analytical totals; presumably a zeolite? [compositionally consistent with wairakite]) traverse the sample. A few large fractured and included zoned REE+Th-bearing fluorapatite crystals are present. Oxides are present as rare scattered baddeleyite and a large thorianite crystal. “Chemical” dating of the thorianite, based on two EPMA spot analyses for Th, U and Pb, gives a mean age of 509±20 Ma, which is consistent with granulite facies metamorphism accompanying the D2 deformation event described for southern Madagascar (for example, see Martelat et al., 2000). This sample bears some similarity to FKM-191 and comes from the same vicinity in Madagascar.
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-205
spinel (Mg0.75Fe2+0.23Zn0.02)(Al1.98Fe3+0.02)O4
thorianite (Th0.74UT0.20PbT0.04Ca0.01Ce4+0.01)O2+x
calcite Ca1.00[CO3]
fluorapatite (main) (Ca4.88Ce0.03La0.01Nd0.01Sr0.01)[P2.97Si0.07O12](F0.95Cl0.05[OH]0.01)
(most REE+Th-rich)
dissakisite-(Ce) Ca1.00(Ce0.46La0.27Ca0.14Nd0.08Pr0.04[M+HREE]0.01)(Al0.96Ti0.03Fe3+0.01)Al1.00
fluoro-pargasite (Na0.57K0.40Ca0.02Sr0.01Ba0.01)Ca2.00(Mg3.58Al0.90Fe3+0.36Ti0.10Fe2+0.06Zr0.01)
diopside (Ca0.97Na0.02Mg0.01)(Mg0.68Al0.19Fe3+0.08Ti0.03Fe2+0.02Zr0.01)[Si1.68Al0.32O5.99F0.01]
VIAl-rich serpentine?
IVAl-free chlorite?
wairakite? (Ca0.79[Na2]0.22)[Al2.32Si3.65O12] . ~2H2O


sample: FKM-206
locality: New Idria District, Diablo Range, San Benito Co., California, USA.
rock type: add rock type.
major mineralogy: specimen acquired for titaniferous andradite (melanite).
(left: unpolarized light; right: under crossed polars)


sample: FKM-207
locality: Eveslogchorr Mtn., Khibiny massif, Kola Peninsula, Russia.
rock type: agpaitic porphyritic aenigmatite albite-nepheline syenite to albite-nepheline urtite.
major mineralogy: Specimen consists of a relatively fine-grained matrix of albite and nepheline in roughly sub-equal proportions; no K-feldspar is present. Large phenocrysts of aenigmatite, astrophyllite and zoned eudialyte (sensu lato) poikiolitically enclosing euhedral nepheline are widespread, along with abundant smaller crystals of aegirine. Of the major minerals, only the eudialyte-group mineral (EGM) shows BSE zoning: the main population of large crudely equant crystals are weakly concentrically zoned from a low z eudialyte (sensu stricto) core through a diffuse higher z eudialyte “middle” zone to an outer diffuse high z ferrokentbrooksite rim. A second additional scattered smaller population (it’s unclear how this population relates to the larger equant grains) are markedly sector(?)-zoned between a low z eudialyte and a high z ferrokentbrooksite. This second population appears to be more extremely lower z and higher z respectively than the comparable compositions of the equant grains. There are also a few tiny slightly zoned eudialyte inclusions in the larger aenigmatite grains, but these do not differ too markedly from the eudialyte of the equant grains. For notes on the assumptions made for the normalization of complex minerals such as astrophyllite and eudialyte, see FKM-14 and FKM-27, respectively.
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-207
ilmenite (Fe2+0.66Mn2+0.31)Ti1.01O3
pyrochlore group ss
(high z inner core)
pyrochlore group ss
(mod z outer core)
pyrochlore group ss
(low z outer sector?)
titanite (Ca0.92Na0.05)(Ti0.93Fe3+0.04Al0.01Nb0.01Zr0.01)(O0.94F0.06)[Si0.99Al0.01O4]
eudialyte group ss
(low z ~core)
eudialyte group ss
(mod z ~inner rim)
eudialyte group ss
(high z ~outer rim)
eudialyte group ss
(sector?; highest z)
eudialyte group ss
(sector?; lowest z)
aegirine (Na0.93Ca0.05Mn2+0.01Mg0.01)(Fe3+0.75Fe2+0.11Al0.06Ti0.06Mg0.02)[Si2.00O6]
lorenzenite (Na1.87Ca0.01)(Ti2.00Nb0.01)O3[Si1.95Fe3+0.04O6]
astrophyllite (K1.68Na0.23Sr0.03Rb0.03?Ba0.02)(Na0.64Ca0.36)(Na0.18Fe2+5.22Mn2+1.06Mg0.42Ti0.09Zn0.02V0.01)
aenigmatite (Na3.90Ca0.06Mn2+0.02Ba0.01)(Fe2+8.31Ti2.14Mn2+1.02Mg0.33Fe3+0.17Zn0.02V0.01)O4[Si11.41Al0.50Fe3+0.09O36]
albite Na0.99[Si2.99Al1.00Fe3+0.01O8]
nepheline (Na1.52K0.340.14)[Si2.13Al1.85Fe3+0.02O8]


sample: FKM-208
locality: Ivigtut cryolite deposit, Ivittuut, Arsuk Fjord, Sermersooq, Greenland.
rock type: granite pegmatite-associated fluoride-rich segregation (mined out in 1987).
major mineralogy: The thin section is almost entirely massive cryolite, with scattered large crystals of siderite (partially altered to undifferentiated banded FeO(OH) and subordinate hematite) and scattered quartz, sphalerite (with ~1880 ppm Cd; with ~324 ppm In; with up to ~700 ppm Ga) and galena (with ~280 ppm Sb). The sphalerite contains undulating or looped strings of small euhedral chalcopyrite inclusion, some of which have small pyrrhotite cores (the latter with ~284 ppm Ni). Additional minor larger chalcopyrite occurs both within the sphalerite and separately in the cryolite. The chalcopyrite contains up to ~191 ppm Sn. Sparse acanthite is associated with the sphalerite. Although at first glance the cryolite appears isotropic under crossed polars, it is in fact weakly birefringent (δ ≈ 0.001) and displays complex twinning and intergrowths (best observed in the lower right side of the image).
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-208
galena Pb1.00S1.00
sphalerite (Zn0.88Fe2+0.12)S1.00
chalcopyrite Cu1.01Fe1.00S2.01
pyrrhotite Fe0.86S1.00
goethite or lepidocrocite
siderite (Fe2+0.96Mn2+0.03)[CO3]


sample: FKM-209
locality: Faria claim, Golconda district, Governador Valadares, Minas Gerais, Brazil.
rock type: granite pegmatite.
major mineralogy: specimen acquired for fluorapatite, betrandite, albite and chlorite.
(left: unpolarized light; right: under crossed polars)


sample: FKM-210
locality: Brumado, Bahia, Brazil.
rock type: uvite-magnesite marble. Metamorphosed Mg-metasomatite(?)
major mineralogy: specimen acquired for uvite and magnesite. Sample FKM-119 is another uvite-bearing sample from Brumado, but in talc rather than magnesite.
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-210
magnetite (Fe2+0.52Mg0.45Mn2+0.03)(Fe3+1.97Al0.02Fe2+0.01)O4
magnesite (Mg0.98Fe2+0.01)[CO3]
tourmaline ss
(most Ca+F-rich)
tourmaline ss
(most Ca+Mg-rich)
tourmaline ss
(most □+Al-rich)
trioct mica ss
trioct mica ss


sample: FKM-211
locality: Kipawa alkaline complex, Les Lacs-du-Témiscamingue, Abitibi-Témiscamingue, Québec, Canada.
rock type: metamorphosed alkali syenite.
major mineralogy: specimen acquired for gittinsite, vlasovite and eudialyte.
(left: unpolarized light; right: under crossed polars)


sample: FKM-212 (billet courtesy of E. Grew, Univ. Maine; sample #2344D)
locality: Mount Riiser-Larsen, Napier Complex, Enderby Land, Antarctica.
rock type: quartz-[K-spar]-[osumilite-(Mg)] granulite. UHT granulite from a presumed sedimentary protolith; peak metamorphism estimated to be ~900 °C and ~7 kbars with low PH2O (roughly ≤0.5 kbars); Grew, 1982.
major mineralogy: The rock consists primarily of very coarse-grained grayish-blue (in hand sample; colorless in thin section) osumilite-(Mg) with subordinate alkali feldspar and finer-grained quartz. Despite (or perhaps due to) the high grade metamorphism, alteration and/or retrograde reaction features of complex very fine-grained intergrowths and symplectites complicate the characterization of some of the minerals. Although for the most part relatively fresh, the osumilite shows both thin alteration veinlets that appear to contain a seemingly homogeneous mixed-layer sheet silicate resembling a “Mg-dominant tosudite” (see the accompanying composition table… the analysis is surprising stoichimetric; is this an incipient “pinite”-style alteration?), as well as coarser sub-parallel bands that are much more mineralogically complex. One of the more interesting features of these coarser bands is a material that normalizes remarkably well to an alkali-free osumilite, although it can also be compositionally represented by a chemical combination of 1 cordierite + 6 quartz. Although the mineral appears phase-homogeneous in BSE imaging, it’s certainly possible that the near-identical BSE response from quartz and low-Fe cordierite could mask an otherwise very fine-scale symplectite of these two minerals. It is nonetheless intriguing, however, to speculate that an “alkali-free osumilite” could be a “transitional” phase between osumilite-(Mg) and cordierite+quartz during alteration or retrograde reaction (with osumilite’s potassium accommodated in an accompanying K-feldspar+cordierite symplectite, also present in the coarse veins). Additionally present in these coarser bands are abundant scattered areas of a fine-grained cordierite+opx symplectite. The opx is variably but significantly Al-enriched, and because of its bright BSE response (it is the most Fe-enriched silicate present), these symplectite areas are easily delineated. The large osumilite grains also have a few scattered inclusions: a few rare small sillimanite crystals (bright white areas in the Al X-ray map), a few rare small magnetite grains, and a few larger isolated cordierite crystals (the latter partially separated from the host osumilite by a rim of alkali feldspar microperthite). Interestingly, one of the large cordierite inclusions itself hosts a phlogopite inclusion (the only one observed in this sample) that is accompanied by opx. The final major phase present in this sample is a meso- to anti-perthitic alkali feldspar. X-ray mapping indicates diffuse zoning of K in the feldspar (notably visible in the large central grain; likely in part be due to pixel-scale averaging of the micro-[meso/anti]-perthitic texture). However, Na(+Ca) become more abundant towards the boundaries of these large alkali feldspar grains, particularly against osumilite, where near end-member albite devoid of anti-perthitic lamellae is observed. Neither garnet, spinel nor sapphirine are present in this particular thin section. For a detailed overview of the general mineralogy, textures, metamorphic reactions and petrogenetic implications of the osumilite-bearing granulites of Enderby Land, Antarctica (including a cursory description of the specific Mount Riiser-Larsen rocks), see Grew, 1982.
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-212
magnetite Fe2+0.98(Fe3+2.00Al0.01)O4
sillimanite (Al1.98Fe3+0.02)O[Si0.97Al0.03O4]
osumilite-(Mg) (K0.910.09)(Na0.141.86)(Mg1.84Fe2+0.15)(Al2.71Fe3+0.18Mg0.11)[Si10.04Al1.96O30]
“K-free osumilite”
(= 1 cordierite +
6 quartz; see text)

or an extremely fine intergrowth (not recognizable in BSE) of cordierite + quartz:

(Mg1.74Fe2+0.22Al0.03)Al3.00[Al1.03Si4.97O18] + 6SiO2

(with “tosudite”)
(with opx in symplectite)
(Mg1.75Fe2+0.17Fe3+0.07)(Al2.99Fe3+0.01)[Al1.09Si4.91O18] . Na0.01
(inclusion in osumilite)
(Mg1.74Fe2+0.22Fe3+0.04)Al3.00[Al1.04Si4.96O18] . Na0.01
“hypersthene” (least Al-rich) (Mg0.99Fe2+0.01)(Fe2+0.60Mg0.31Al0.07Fe3+0.02)[Si1.91Al0.09O6]
“hypersthene” (most Al-rich;
with cordierite in symplectite)
phlogopite (K0.83Na0.010.16)(Mg2.49FeT0.35Al0.16)[Si2.99Al1.01O10]([OH]1.41F0.58)
“Mg-dominant tosudite”? (Mg0.29K0.21Ca0.04Na0.03)(Al3.85Mg1.70FeT0.45)[Si7.04Al0.96O18]([OH]11.99Cl0.01) . ~5H2O
K-feldspar (with
cordierite in symplectite;
-29.1% admixed cordierite)
alkali feldspar
(main; mesoperthitic)
albite (see text) (Na0.94Ca0.03K0.01)[Si2.94Al1.06O8]


sample: FKM-213 (billet courtesy of Z. Mcintire, Univ. Washington)
locality: near Erbareti, Vercelli province, Piemonte, Italy.
rock type: originally purported to be a charnockite, cursory inspection suggests the rock is an orthopyroxene-free garnet-bearing gneiss.
major mineralogy: specimen acquired for orthopyroxene.
(left: unpolarized light; right: under crossed polars)


sample: FKM-214
locality: Hålsjöberg, Torsby, Värmland, Sweden.
rock type: test.
major mineralogy: specimen acquired for wagnerite and lazulite. A cluster of three fairly small (~50 μm) weakly zoned Zr-bearing pretulite crystals occur adjacent to and near a mildly Sc-enriched (~1.2 wt%) zircon. The precise Zr concentration of the pretulite was challenging to determine due to the small grain size, potential fluorescence from the adjacent zircon, and the significant overlap of the P Kβ x-ray line on the Zr Lα line; a PET crystal was used for the Zr measurement (instead of the usual higher sensitivity TAP crystal) to thin the peaks a bit and nominally reduce the overlap. The HREE content was estimated from a simple linear REE pattern extrapolation from Gd to bring the overall total close to 100%; Er and Yb will be subsequently measured to check this. A single anhydrite crystal was identified within a larger wagnerite crystal.
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-214
pyrite Fe1.00S2.00
rutile (Ti0.97V~0.02Fe3+0.01)O2
hematite (Fe3+1.84Ti0.08Fe2+0.08Al0.01)O3
anhydrite (Ca0.96Sr0.03)[S1.01O4]
pretulite (Sc0.86Zr0.08Y0.04[HREE]~0.01)[P1.00Si0.01O4]
wagnerite (most Mg+F-rich) (Mg1.87Fe2+0.06Mn2+0.05Fe3+0.03)(F~0.82[OH]~0.18)[P0.99O4]
wagnerite (most Fe+[OH]-rich) (Mg1.52Fe2+0.42Mn2+0.06)(F~0.61[OH]~0.39)[P1.00O4]
kyanite (Al1.99Fe3+0.01)O[Si0.98Al0.02O4]


sample: FKM-215
locality: Saranovskii mine, Saranovskaya village, Permskaya Oblast’ (middle Ural Mtns. region), Russia.
rock type: hydrothermally altered and metamorphosed chromitite.
major mineralogy: specimen acquired for chromian amesite and chromite.
(left: unpolarized light; right: under crossed polars)


sample: FKM-216
locality: Långban, Filipstad, Värmland, Sweden.
rock type: richterite-augite-[Mn-calcite] metasomatite.
major mineralogy: The specimen was acquired for caryinite, but caryinite does not appear to be present in the sample. The rock is one of the skarn-like Mn-rich metasomatites typical of the Värmland region Långban-type deposits. Mn-rich calcite makes up most of the rock, with subordinate colorless Mn-bearing richterite and larger orange-brown clinopyroxene zoned from aegirine-augite in the more deeply colored core to a considerably less Na-enriched less-strongly colored main augite mantling composition. Iwakiite (anisotropy verified; also present in sample FKM-242 from the nearby and genetically-similar Nordmark mine; compare with jacobsite, the spinel polymorph of Mn2+Fe3+2O4 in sample FKM-243 from Bald Knob, NC, USA) is also widely present. Minor scattered barite is present, as is a moderately zoned Pb-bearing johnbaumite as the representative apatite-group mineral (and only significant As-bearing species) in the sample. Clusters of widely-scattered but relatively small fluorcalcioroméite are notable and also represent the only significant Sb mineral present. The fluorcalcioroméite are markedly zoned, with commonly (but not invariably) low z cores and more irregularly zoned moderate and higher z areas. The lowest z zones closely approach hydroxycalcioroméite in composition, while the highest z zones approach fluornatroroméite; it is possible localized compositional zones corresponding to these end-members could be exist in unanalyzed portions of the material. Of course roméite group minerals, as members of the pyrochlore supergroup, present some notable analytical challenges, including variable valences of Fe (and Mn?), potential vacancies in multiple possible sites, and molecular H2O also in multiple possible sites. For a more detailed description of how the normalization of pyrochlore group minerals has been treated to address these complications, see the discussion under sample FKM-41, a sample with abundant hydroxycalciopyrochlore from the Oka carbonatite.
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-216
iwakiite (most Mn-rich) (Mn2+0.97Mg0.02Zn0.01Ca0.01)(Fe3+1.15Mn3+0.84)O4
iwakiite (most Fe-rich) (Mn2+0.97Mg0.02Zn0.01)(Fe3+1.38Mn3+0.61)O4
fluorcalcioroméite (low z; some cores) (Ca1.14Na0.24Y0.01[H2O]~0.50~0.11)
fluorcalcioroméite (mod z) (Ca1.03Na0.47Y0.01[H2O]~0.16~0.32)
fluorcalcioroméite (high z) (Ca0.99Na0.83Y0.020.16)
calcite (Ca0.90Mn2+0.10)[CO3]
barite (Ba0.98Ca0.01)[S1.00O4]
johnbaumite (most F-rich) (Ca4.70Pb0.21Mn2+0.04Sr0.01Ba0.01Na0.01)[As2.93P0.06S0.01O12]([OH]0.74F0.25)
johnbaumite (most Pb-rich) (Ca4.68Pb0.24Mn2+0.05Sr0.01Ba0.01Na0.01)[As2.92P0.06S0.01Si0.01O12]([OH]0.86F0.13)
aegirine-augite-rich cpx ss (core) (Ca0.59Na0.33Mn2+0.08)(Mg0.60Fe3+0.30Mn2+0.06Mn3+0.04)[Si1.98Fe3+0.01O6]
augite-rich cpx ss (main mantle) (Ca0.75Na0.14Mn2+0.11)(Mg0.76Fe3+0.12Mn2+0.08Mn3+0.03)[Si1.98Fe3+0.01O6]
richterite (Na0.65K0.200.15)(Na0.97Ca0.88Mn2+0.15)(Mg4.27Mn2+0.50Fe3+0.14Mn3+0.09)


sample: FKM-217
locality: Tanco pegmatite mine, Bernic Lake, Lac-du-Bonnet area, Manitoba, Canada.
rock type: test.
major mineralogy: specimen acquired for wodginite, microcline and lithian muscovite.
(left: unpolarized light; right: under crossed polars)


sample: FKM-218
locality: Üdersdorf, Daun, Eifel, Rhineland-Palatinate, Germany (the sample is consistent with the rocks from the “basalt” quarries in the Löhley area, roughly 0.8 km NW of Üdersdorf).
rock type: olivine-clinopyroxene-leucite nephelinite notably enriched in Ba. This mafic rock probably represents a low degree of partial melting of metasomatized mantle.
major mineralogy: The rock is largely composed of a relatively fine-grained groundmass of nepheline and weakly-zoned diopside. Larger phenocrysts of more strongly optically-zoned diopside are abundant, and smaller and less abundant forsterite phenocrysts are also present. In some cases, somewhat irregular and borderless (in BSE; partially resorbed relict?) forsterite occurs as inclusions in the diopside. Abundant Ti-rich magnetite is the dominant oxide phase present, although additional oxides include minor tiny Fe+Al-rich euhedral magnesiochromite crystals, scattered zoned Nb-bearing perovskite, minor amounts of a potentially new magnetoplumbite group mineral approximately along the batiferrite-haggertyite join, and a small single observed grain of possible calzirtite (although less plausibly, the material can also be normalized to a hypothetical [2Zr+1Ti] zirconolite end-member). Additional minor accessory phases include scattered markedly zoned Ba+Ti-rich phlogopite; small clusters of fresnoite crystals typically attached to magnetite; and associated with one of these fresnoite clusters, a single blade of a lamprophyllite group mineral resembling lileyite (but with Fe2+ > Na at the M2 site), or alternatively considered as resembling a Fe2++Mg-rich variety of schüllerite akin to that observed by Rastsvetaeva et al., 2016 from this locality. Zoned fluorapatite is also present with markedly Sr-enriched rims (note: the apatite shown in the composition table was only ~20 μm away from a large magnetite crystal, so the reported Fe contents may in part be due to secondary fluorescence from the adjacent oxide; hence the “?” accompanying the Fe apfu). Both the hand sample and the thin section show the vesicular nature of the rock, and partial in-filling of the open space with residual melt illustrates a somewhat different assemblage from the host groundmass. Most notable are large leucite crystals, which are intergrown with less prevalent nepheline, additional diopside (some almost anhedral filling space between leucite crystals), and larger magnetite and fluorapatite crystals. Also present are scattered zeolite pseudomorphs after some unknown mineral; these pseudomorphs are irregular intergowths of what appears to be an Fe-bearing clinoptilolite-Ca along with another phase with a higher Si:Al ratio, lower apfu of non-framework cations and higher water content (and not successfully normalizable). In addition to the abundant leucite in the more open-space portions of the sample, rare crystals of leucite also occur as inclusions in diopside phenocrysts; in one case, a relatively large leucite inclusion in diopside itself hosted several small inclusions of haüyne. For a discussion of the challenges and assumptions used for the normalization of S-bearing sodalite-group minerals such as haüyne, see the note concerning lazurite in the description of sample FKM-25.
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-218
pyrrhotite (Fe0.91Ni0.01)S1.00
magnetite (Fe2+0.67Mg0.27Mn2+0.05)(Fe3+1.10Ti0.42Fe2+0.42Al0.04V0.02)O4
magnesiochromite (Mg0.55Fe2+0.42Mn2+0.01)(Cr0.90Al0.62Fe3+0.36Ti0.06Fe2+0.06)O4
(most Na+Nb-rich)
(most Ca+Ti-rich)
(magnetoplumbite group)
calzirtite? (Ca1.54Y0.11Mn2+0.09U0.06Mg0.05Fe2+0.04[HREE]0.03Sr0.02Ba0.01)
fluorapatite (core) (Ca4.88Sr0.05Fe2+0.02?Na0.01Ce0.01La0.01)[P2.91Si0.07S0.01O12](F0.74[OH]0.23Cl0.03)
fluorapatite (rim) (Ca4.35Sr0.55Na0.04Fe2+0.03?Ce0.02La0.01)[P2.95Si0.03S0.01V0.01?O12](F0.76[OH]0.23)
forsterite (large
phenocrysts “main”)
forsterite (“wisps” in
large phenocrysts)
forsterite (partially
resorbed in cpx)
fresnoite (Ba1.82Sr0.13Ca0.05Na0.02K0.01)(Ti0.93V0.08)O[Si1.93Fe3+0.04Al0.01O7]
M2Fe-dominant lileyite”
or similar to the
“Fe2++Mg-schüllerite” of
Rastsvetaeva et al., 2016
(zoned phenocryst;
core; higher z)
(zoned phenocryst;
core; lower z)
(zoned phenocryst;
main mantle)
(zoned phenocryst;
thick inner rim)
(zoned phenocryst;
thin outermost rim)
(inclusion in olivine)
(groundmass; main)
diopside (open-space
filling with leucite)
(most Ba+Ti-rich;
some central stripes)
(main “core”)
(most F-rich; tips)
(most K+Si-rich; tips)
nepheline (Na0.73K0.27)[Si1.01Al0.97Fe3+0.02O4]
leucite (K0.98Ba0.01)[Si1.98Al1.00Fe3+0.02O6]
haüyne (in leucite
in cpx phenocryst)
(Na4.66K1.34Mg0.01)[Si5.95Al6.02P0.03O24] . (Na0.76Ca0.36Sr0.08Ba0.01)
(Cl0.53[H2SOx; x = 3, 4]0?0.52?[SO4]2-0.45?[S3?]2-0.11?F0.01)
(higher z areas
in mixed zeolite)
(Ca1.21[K2]0.32Mg0.30Ba0.14Sr0.03[Na2]0.01)[Si13.03Al3.64Fe3+1.32P0.01O36] . ~11-12H2O


sample: FKM-219
locality: Anna mine, Horní Planá (by Mariánské Lázně), Czech Republic; (uncertain, but could be this or this locality… both contain Fe-Ni arsenide and uranium mineralization, although neither locality notes any observed V minerals).
rock type: test.
major mineralogy: specimen acquired for roscoelite.
(left: unpolarized light; right: under crossed polars)


sample: FKM-220
locality: Pacific Limestone Products Quarry (Kalkar Quarry), Santa Cruz, Santa Cruz Co., California, USA.
rock type: tremolite-diopside calc-silicate. The locality is described as a “limestone” quarry, but in this sample the original limestone has been strongly metasomatized to a calc-silicate rock. The unique mineralogy is the result of the introduction of Ba, Sn, Ti, U, As, Sb and Ni (among a variety of other elements). Slight localized alteration of the diopside to gypsum (see below) and lack of detectable Sn in any of the calc-silicates suggests that the introduction of sulfur and some of the other rarer elements may have occurred after the main tremolite + diopside development
major mineralogy: The specimen was specifically acquired for pabstite, which occurs as a few millimeter-sized irregular masses in one corner of the sample; these were originally roughly located in the thin section by their bright blue-white fluorescence under SWUV (and subsequently once in the microprobe, the grains were more precisely located by their brilliant blue-white CL). The material is weakly zoned. Of interest due to potential solid solution with bazirite (for example, see bazirite-bearing samples FKM-53 and FKM-53b from the Madrelena mine, Tres Pozos, Baja California Norte, Mexico), Zr contents in the most Ti-rich portions of the pabstite reach ~150 ppm Zr, but drop to below detection in the more Sn-rich portions. In addition to the abundant calcite, the dominant silicate in the sample is a weakly zoned diopside (in some places slightly altered by thin veinlets of gypsum). The diopside shows a notable blue-white CL in the more Mg-rich portions which is more subdued in the more Fe-rich portions. Subordinate unzoned tremolite is also present. No detectable Sn is observed in either the diopside or the tremolite. Scattered large zoned celsian crystals (blue-white CL) are present; these are essentially very Ba-rich, with only small irregular swirls, patches and wisps showing higher K contents. Seemingly unzoned and relatively large apatite crystals, close to the fluorapatite-hydroxylapatite composition boundary, are scattered throughout the sample. Quartz is also scattered in the sample and appears to be primarily a relict material (sand? chert?) from the original limestone. Coarse galena with slight Ag- and Bi-enrichment is dominant sulfide in the sample. Small rounded and fairly “ratty” pyrite is also present; curiously, some of these grains are grown around a small core of low-Th uraninite. The minor sulfosalts and rare Ba-Ti minerals such as taramellite that the locality is also known for may possibly be present in this sample, but were not obvious under BSE. This is in part due to the challenges of differentiating among the abundant tiny high z phases widespread in the sample; X-ray mapping for specific elements of interest such as As, Sb, Ti, and Ba could potentially uncover some of these additional minerals. Sample FKM-238 is from the same locality, but contains Ba-mica rather than Ba-feldspar + pabstite, more carbonate compared to silicates, and also a different and less conspicuous sulfide assemblage.
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-220
galena (Pb0.99Ag0.01Bi0.01)S1.00
pyrite (with UO2 “core”;
most Ni+As-rich)
pyrite (with UO2 “core”;
most Sb-rich)
pyrite (no UO2 “core”) Fe0.99S1.99
uraninite (U4+0.90U6+0.04Ca0.02Th0.01Pb0.01)O2
calcite (Ca0.98Mg0.01)[CO3]
fluorapatite-rich apatite ss (Ca4.95Sr0.01)[P2.99O12](F0.57[OH]0.41Cl0.03)
hydroxylapatite-rich apatite ss (Ca4.95Sr0.01Y0.01)[P2.99Si0.01O12]([OH]0.48F0.47Cl0.04)
pabstite (most Ti-rich) (Ba1.04Na0.01)(Sn0.77Ti0.23)[Si3.00O9]
pabstite (most Sn-rich) (Ba1.03Na0.01)(Sn0.87Ti0.17)[Si3.00O9]
diopside (most Mg-rich) Ca0.99(Mg0.96Fe2+0.02)[Si2.02O6]
diopside (most Fe-rich) Ca0.98(Mg0.87Fe2+0.12)[Si2.01O6]
tremolite (K0.010.99)(Ca1.95Na0.01)(Mg4.54Fe2+0.37Fe3+0.05Al0.01Mn2+0.01)[Si8.01O22]([OH]1.95F0.05)
(main in most Ba-rich xtls)
celsian (main in other xtls) (Ba0.87K0.16Na0.01Ca0.01)[Si2.19Al1.80O8]
celsian (most K-rich) (Ba0.74K0.27Na0.02Ca0.01)[Si2.31Al1.69O8]


sample: FKM-221
locality: Little Green Monster mine, Clay Canyon, Fairfield, Utah Co., Utah, USA.
rock type: phosphatic nodules in limestone.
major mineralogy: specimen acquired for variscite, crandallite, wardite and kolbeckite.
(left: unpolarized light; right: under crossed polars)


sample: FKM-222
locality: near Mama River, Buryatia, Pribaikal’e, Eastern Siberian region, Russia.
rock type: test.
major mineralogy: specimen acquired for lazulite and muscovite.
(left: unpolarized light; right: under crossed polars)


sample: FKM-223
locality: Kuannersuit Plateau (Kvanefjeld), Ilímaussaq complex, Narsaq, Kujalleq, Greenland.
rock type: test.
major mineralogy: specimen acquired for neptunite.
(left: unpolarized light; right: under crossed polars)


sample: FKM-224
locality: Poços de Caldas, Poços de Caldas alkaline complex, Minas Gerais, Brazil.
rock type: khibinite.
major mineralogy: specimen acquired for manganoeudialyte. “Orvillite” is a term coined by Lee, 1919 [← link is an open source American Mineralogist “new minerals” summary of a subscription-required American Journal of Science article] to describe hydrated zirconium silicate altering from baddeleyite at Poços de Caldas. This material appears broadly similar, but altering from eudialyte (sensu lato) along thin cracks and crevices, although also from the same locality. It is a presumably impure and amorphous mineraloid, and may be akin to a zirconium equivalent of now-discredited “thorogummite” Piilonen et al., 2015 [← abstract]. The material has been normalized to ∑(M+T)=2-x, where x is an estimate of T-site vacancies (also equals 4H; this is akin to the hydrogarnet exchange of [4H+1vac] for 1Si), sufficient to charge balance the overall formula. Estimated excess integral H2O was added to bring the total to near 100%.
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-224
~”orvillite”? (see text) (Zr0.84Ca0.05Ti0.04Nb0.03MnT0.01Ce0.01La0.01)[Si0.76Al0.12Fe3+0.04~0.06O~3.76(OH)~0.24] . ~2H2O
lamprophyllite (Sr1.26Na0.40K0.24Ba0.07){Na1.00(Na1.36Mn2+0.56Ca0.08)(Ti0.88Nb0.07Mg0.05)(O0.91F0.68[OH]0.41)}
~[kochite]-[götzenite] join (Ca3.64Sr0.04Ce0.03La0.02Y0.02Nd0.010.24){Na1.00(Na1.19Zr0.57Mn2+0.20FeT0.03Hf~0.01)([OH]1.01O0.62F0.37)}
eudialyte group ss (#62;
main; estimated z̄ ≈ 13.00)
eudialyte group ss
(#10; main; most Fe-rich;
estimated z̄ ≈ 15.39)
eudialyte group ss (#60; rim
on #62; most Mn+REE-rich;
estimated z̄ ≈ 16.20)
eudialyte group ss (#16; high
z patches in #10 & #60;
estimated z̄ ≈ 16.36)
wadeite K1.99(Zr1.00Hf~0.01)[Si2.97Ti0.02O9]
(Na0.87K0.59[H3O]+~0.52Ca0.01Y0.01)(Zr0.98Nb0.01Hf~0.01)[Si2.97Al0.01Ti0.01O9] . 2H2O
aegirine (most Ca+Mg-rich) (Na0.94Ca0.07)(Fe3+0.88Mg0.06Ti0.02Al0.02Mn2+0.01Mn3+0.01)[Si1.99Al0.01O6]
aegirine (most Mn+Ti-rich) (Na0.96Ca0.05)(Fe3+0.78Ti0.09Mg0.05Mn2+0.03Fe2+0.02Al0.01)[Si1.98Al0.02O6]
aegirine (most Na+Al-rich) (Na0.99Ca0.01)(Fe3+0.84Al0.12Ti0.01Mn2+0.01Mn3+0.01)[Si1.99Al0.01O6]
chamosite Ca0.03(FeT2.51MnT1.45Al1.41Zr0.19Mg0.05Ti0.020.35)[Si2.64Al1.36O10]([OH]7.57O0.43)
orthoclase (most K-rich;
vuggy areas)
orthoclase (most Na-rich;
clean areas)
nepheline (Na3.02K0.97)[Si3.98Al3.98Fe3+0.04O16]
analcime (Na1.10Ca0.03K0.01)[Si1.73Al1.26O10] . ~0.86H2O
natrolite? ([Na2]0.70Ca0.33Sr0.06)[Si2.67Al2.33O10] . ~2H2O


sample: FKM-225
locality: Kaznakhtinskii massif, Ust’-Koksa district, Gorno-Altayskaya Autonomous Oblast’, Western Siberian region, Russia.
rock type: test.
major mineralogy: specimen acquired for chromian iowaite and serpentine.
(left: unpolarized light; right: under crossed polars)


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