samples FKM-301 to FKM-325

 

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.

Note: Depending on the speed of your internet connection, it could take a minute or two for the images to load.

 


muirite and sanbornitemuirite and sanbornite

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

sample: FKM-301
locality: Esquire No. 7 claim, Big Creek, Rush Creek deposit, Big Creek-Rush Creek district, Fresno Co., CA, USA.
rock type: test.
major mineralogy: The specimen was acquired for muirite and sanbornite.

 



harkerite and monticellite in marbleharkerite and monticellite in marble

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

sample: FKM-302
locality: Kilbride, Isle of Skye, Scotland, UK.
rock type: test.
major mineralogy: The specimen was acquired for harkerite and monticellite.

 



Franklin minerals in thin sectionFranklin minerals in thin section

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

Franklin minerals in thin section under UV light

under shortwave ultraviolet [SWUV] illumination

 
sample: FKM-303
locality: Franklin, Franklin mining district, Sussex Co., NJ, USA.
rock type: hardystonite-andradite-bustamite “metasomatite”. Granulite facies Zn-Mn-metasomatite..
major mineralogy: Large euhedral bustamite (essentially none to weak turquoise-colored SWUV fluorescence) and subhedral andradite garnet dominate the sample. Interstitial abundant hardystonite (strong blue SWUV fluorescence and cathodoluminescence) and lesser abundance “jeffersonite” clinopyroxene (near-boundary diopside-johannsenite compositions with an additional significant petedunnite component) are also present. Under BSE imaging, the hardystonite shows a main lower-z zone (enriched in Al and Na), and widespread higher-z patches enriched in Pb and Sr. Sparse inclusions of what appears to be hydro-andradite occur with the main andradite. Minor willemite is widely scattered in the sample, as inclusions in garnet and as streaks along fractures in the bustamite; the willemite is strongly cathodoluminescent and SWUV fluorescent in yellow-green (except apparently for one grain included in the “video” andradite, which while strongly cathodoluminescent appeared to lack any significant fluorescence). Sparse clinohedrite (orangish cathodoluminescence) occurs as small lone inclusions in garnet and as rims on willemite in garnet. Additional minor minerals include a single larger franklinite, one cluster of johnbaumite (orange cathodoluminescence; occurring with willemite in garnet), sparse calcite (red-orange cathodoluminescence; also in garnet) and scattered tiny barite.
accompanying videos: Short videos featuring the mineral associations and optical properties of the andradite, hardystonite, “jeffersonite” and bustamite in this thin section offer a more detailed look at this sample.

mineral representative mineral compositions in FKM-303
franklinite (Zn0.74Mn2+0.26)(Fe3+1.71Al0.16Mn3+0.11Ti0.01Mg0.01)O4
calcite (Ca0.98Mn2+0.02)[CO3]
barite not analyzed
johnbaumite (Ca4.88Ce0.04Sr0.02Mn2+0.02Na0.01Pb0.01La0.01Nd0.01)[As0.833P0.15Si0.01S0.003V0.003O4]3([OH]0.82F0.18)
willemite (most Zn+Fe-rich;
essentially no fluorescence)
(Zn0.93Mn2+0.04Mn3+0.02)Zn1.00[Si0.98Fe3+0.02O4]
willemite (intermediate Mn;
relatively brighter CL)
(Zn0.88Mn2+0.10Mg0.02)Zn1.00[Si1.00O4]
willemite (most Mn-rich;
relatively dimmer CL)
(Zn0.80Mn2+0.17Mg0.02Mn3+0.01)Zn1.00[Si1.00O4]
andradite (Ca2.40Mn2+0.59Mg0.01)(Fe3+1.54Al0.44Zn0.01)[Si0.997As0.003O4]3
“hydro-andradite” (Ca2.92Mn2+0.05Mg0.03)(Fe3+1.29Al0.53Mn3+0.15Zn0.02Ti0.01)[Si0.940.06O3.76(OH)0.22F0.02]3
clinohedrite (Ca0.95Mn2+0.05)Zn1.00[Si0.99Fe3+0.01O4] . H2O
hardystonite (main;
most Na+Al-rich)
(Ca1.93Na0.06)(Zn0.92Al0.06Mg0.01Mn2+0.01)[Si1.99Al0.01O7]
hardystonite (patchy;
most Zn+Pb-rich)
(Ca1.95Pb0.04Sr0.01)(Zn0.98Al0.01Si0.01)[Si2.00O7]
diopside-dominant cpx ss
(“jeffersonite”; adjacent to
bustamite+hardystonite)
(Ca0.94Mn2+0.04Na0.02)(Mg0.48Mn2+0.35Zn0.13Fe3+0.04Mn3+0.01)[Si1.97Al0.01Fe3+0.01O6]
johannsenite-dominant cpx
ss (“jeffersonite”; adjacent
to bustamite+andradite)
(Ca0.97Mn2+0.01Na0.01)(Mn2+0.46Mg0.41Zn0.11Fe2+0.02)[Si2.01O6]
bustamite Ca1.00(Ca0.83Mn2+0.17)Mn2+1.00(Mn2+0.77Mg0.14Zn0.09)[Si4.00O12]

 



kraisslitekraisslite

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

Franklin minerals in thin section under UV light

under shortwave ultraviolet [SWUV] illumination

 
sample: FKM-304
locality: Sterling Hill, Ogdensburg, Franklin mining district, Sussex Co., NJ, USA.
rock type: test.
major mineralogy: The specimen was acquired for kraisslite and franklinite. Numerous samples from the Franklin and Sterling Hill areas are represented among this collection; however, the only other arsenate-bearing sample is FKM-317, a sample from the Franklin mine containing one or potentially more members of the chlorophoenicite group.

 



pyrochlore and katophorite in syenitepyrochlore and katophorite in syenite

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

sample: FKM-305
locality: Água de Pau Massif, São Miguel Island, Azores, Portugal.
rock type: test.
major mineralogy: The specimen was acquired for fluornatropyrochlore and ferro-katophorite.
accompanying videos: Short videos featuring the mineral associations and optical properties of the ferro-ferri-fluoro-katophorite and zircon in this thin section offer a more detailed look at this sample.

mineral representative mineral compositions in FKM-305
ilmenite (Fe2+0.88Mn2+0.10Fe3+0.02)(Ti0.94Fe3+0.03Nb0.02V0.01)O3
magnetite analysis pending
fluorcalciopyrochlore
(most Ca+Nb-rich;
lowest z)
(Ca0.89Na0.72Ce0.09Nd0.05U0.03Th0.02Y0.02La0.02[HREE]~0.02Pr0.01Sm0.01Gd0.01Mn2+0.01[H2O]~0.10?)
(Nb1.51Ti0.39Ta0.06FeT0.02Zr0.01)(O5.90[OH]0.10)(F0.72[OH]0.28)
fluorcalciopyrochlore
(mod z)
(Ca0.86Na0.73Ce0.10Nd0.06Th0.04[HREE]~0.03Y0.03La0.02Sm0.02Gd0.02Pr0.01U0.01Mn2+0.01[H2O]~0.06?)
(Nb1.44Ti0.41Ta0.07Zr0.05FeT0.02Sn0.01)(O5.97[OH]0.03)(F0.72[OH]0.28)
fluorcalciopyrochlore
(most [M+HREE-rich;
highest z)
(Ca0.85Na0.72Ce0.10Nd0.06Th0.05[HREE]~0.04Y0.04La0.02Sm0.02Gd0.02Pr0.01U0.01Mn2+0.01[H2O]~0.05?)
(Nb1.42Ti0.40Ta0.09Zr0.06FeT0.02Sn0.01)(O5.98[OH]0.02)(F0.69[OH]0.31)
apatite analysis pending
zircon not analyzed
chevkinite-(Ce)
(most Ca+Ti-rich;
lowest z)
(Ce1.69La0.99Ca0.69Nd0.33Pr0.14Th0.04[HREE]~0.04Y0.03Sm0.03Gd0.02)
(Fe2+0.72Mg0.08Zr0.07Mn2+0.06Ca0.05)(Ti0.64Fe2+0.56Fe3+0.51Nb0.21Al0.05V0.02)
Ti2.00O8.00[Si1.995Al0.005O7]2
chevkinite-(Ce)
(most REE+Fe-rich;
highest z)
(Ce1.82La0.93Nd0.44Ca0.41Pr0.17Sm0.05Th0.05[HREE]~0.05Y0.04Gd0.03Na0.01)
(Fe2+0.84Mn2+0.11Ca0.03Zr0.02)(Fe2+0.70Fe3+0.54Ti0.41Nb0.32V0.02Ta0.01)
Ti2.00O8.00[Si1.985Al0.01O7]2
diopside (most Mg-rich; main) (Ca0.87Na0.06Mn2+0.04Mg0.02)(Mg0.63Fe2+0.29Fe3+0.06Al0.01Ti0.01)[Si1.96Al0.04O6]
diopside (most Fe-rich; rim) (Ca0.89Na0.07Mn2+0.04)(Mg0.53Fe2+0.39Fe3+0.07Ti0.01)[Si1.98Al0.02O6]
fluoro-pargasite
(Hawthorne et al., 2012)
or alternatively fluoro-edenite
(Leake et al., 1997)
(Na0.77K0.23)(Ca1.68Na0.32)(Mg3.03Fe2+1.19Fe3+0.41Ti0.17Mn2+0.12Al0.05Na0.03)
[Si6.88Al1.12O22](F1.34O0.33[OH]0.32Cl0.01)
ferro-ferri-fluoro-katophorite-dominant B(NaCa)-amph ss
(core; most Al-rich)
(Na0.83K0.17)(Ca1.25Na0.67Mn2+0.08)(Fe2+2.31Mg1.69Fe3+0.59Ti0.22Mn2+0.14Al0.04Zn0.01)
[Si7.03Al0.97O22](F0.96[OH]0.58O0.45Cl0.02)
ferro-ferri-fluoro-katophorite-dominant B(NaCa)-amph ss
(main; most Fe-rich)
(Na0.74K0.25)(Ca1.23Na0.67Mn2+0.11)(Fe2+3.33Mg1.02Fe3+0.25Ti0.19Mn2+0.18Zn0.01)
[Si7.40Al0.56Fe3+0.03O22](F0.94[OH]0.67O0.38Cl0.01)
ferro-ferri-katophorite-dominant B(NaCa)-amph ss (rim) (Na0.75K0.24)(Ca0.98Na0.87Mn2+0.15)(Fe2+3.68Mg0.46Fe3+0.45Ti0.21Mn2+0.18Zn0.02)
[Si7.41Al0.53Fe3+0.06O22]([OH]0.87F0.70O0.41Cl0.02)
“biotite” (K0.92Na0.09)(FeT1.61Mg1.01Ti0.25MnT0.07Zn0.010.05)[Si2.93Al1.03O10]([OH]0.84F0.65O0.51Cl0.01)
“Na-sanidine” (Na0.64K0.35)[Si2.98Al1.00Fe3+0.01O8]
“alkali-silicate”
(K-dominant material)
~(K0.54Na0.42Ca0.04Y0.02)(Al1.14Fe2+0.68Zr0.08Mn2+0.06Ti0.02Zn0.02)[Si9.90Al0.10O22]
([OH]1.35O0.36F0.19Cl0.10)
“alkali-silicate”
(Na-dominant material)
~(Na0.74K0.54Ca0.02Y0.02)(Al1.08Fe2+0.66Zr0.14Mn2+0.06Ti0.04Zn0.02)[Si9.82Al0.18O22]
([OH]0.98O0.70F0.23Cl0.09)
quartz not analyzed

 



staurolite schiststaurolite schist

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

sample: FKM-306
locality: Semiostrov’e, Keivy Mountains, Murmansk Oblast, Russia.
rock type: test.
major mineralogy: The specimen was acquired for staurolite.

 



yoderite and kyaniteyoderite and kyanite

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

sample: FKM-307
locality: Mautia Hill, Kongwa, Kongwa District, Dodoma Region, Tanzania.
rock type: Because the original sample was essential a large crystal of Mg-orthoamphibole (anthophyllite-gedrite join), the precise nature of the greater rock type from which this specimen was recovered is subject to significant conjecture. However, mineralogically, it would appear to be from a moderate-grade metamorphic rock of likely an overall fairly Mg-rich bulk composition; similar Mg-rich rocks (although generally also considerably more Al-rich; i.e. kyanite-bearing), and of comparable and higher metamorphic grades, are well-known from this classic whiteschist locality. Although anthophyllite is described from some of the kyanite+talc whiteschists (for example, see Jöns & Schenk, 2004; also Chapter 5 in Jöns’ 2006 dissertation), this occurrence of very coarse Mg-orthoamphibole with some minor yoderite and talc (and also absent of all kyanite and quartz, at least at the scale of this sample) seems to be a quite atypical paragenesis, compared to the literature descriptions of anthophyllite at Mautia Hill. Since the entire Mautia Hill complex is presumed to have experienced a similar P-T path, however, perhaps the peculiarities of this specimen do not need to indicate an unusual retrograde reaction within the talc-kyanite whiteschist per se, but may rather alternatively represent a different protolith composition, for example a Mg-metasomatic rock formed along the contact of the kyanite-talc whiteschist with an adjacent Mg-rich rock (e.g. dolomitic marble)? Although outcrops overall are fairly limited in the Mautia Hill area, there do appear to be a few areas where such a contact may be exposed (for an overview geologic map of the locality with superimposed outcrop exposures, see Cutten et al., 2006). In any case, the plausibility of any conjecture on this unique specimen’s origins notwithstanding, some further insight into its petrogenesis could indeed be forthcoming: the dealer from whom I acquired the sample collected it himself, and so if I have an opportunity to speak with him at the next Tucson Gem & Mineral Show, I’ll be sure to ask him about it and to update this section with any additional information he can offer.
major mineralogy: The specimen was acquired for “green yoderite”. However, the sample appears to be just a large crystal of Mg-orthoamphibole (optically continuous; see crossed polarizer thin section scan), with scattered large yoderite inclusions, minor talc, rare small zircon, and notably (in the PPL thin section scan) abundantly-included with small to moderate-sized hematite and rutile; no kyanite or quartz are present. The amphibole crystal is internally shattered and was quite friable, resulting in some challenge in preparing the thin section billet. Compositionally, the amphibole has (B+C)[Mg/(Mg+Fe2+)] = ~0.93, along with 0.95 apfu TAl and 0.85 apfu CAl; this composition falls almost exactly halfway along the anthophyllite-gedrite join. Indeed, unlike some other aluminous orthoamphiboles where TAl incorporation is accompanied by concomitant ANa incorporation, this material contains almost no Na. The yoderite within the amphibole is nearly colorless in thin section, and so is visually distinct (and less striking) from the better-known indigo/purple yoderite variety, also found at Mautia Hill and intimately associated with kyanite and talc (featured here in samples FKM-69 and FKM-69b); nonetheless, the composition of this “pale green” yoderite differs only slightly from that of the indigo/purple yoderite in the other samples (primarily in minor Mn and Cr differences).
accompanying videos: Short videos featuring the mineral associations and optical properties of the green yoderite and anthophyllite in this thin section offer a more detailed look at this sample.

mineral representative mineral compositions in FKM-305
rutile Ti0.99O2
hematite (Fe3+1.86Ti0.06Fe2+0.06Al0.02Cr0.01)O3
zircon not analyzed
yoderite (Mg1.95Fe2+0.04Al0.01)(Al5.61Fe3+0.38Cr0.01)O2[Si0.988P0.075Al0.005O4]4([OH]1.99O0.01)
anthophyllite-gedrite join
B(MgMg)-orthoamph ss
1.00(Mg1.70Fe2+0.12Ca0.09Mn2+0.05Na0.04)(Mg4.00Al0.85Fe3+0.13Ti0.01)
[Si7.05Al0.95O22]([OH]1.96F0.02O0.02)
talc Ca0.01(Mg2.78Al0.15FeT0.03Ti0.010.03)[Si3.86Al0.14O10]([OH]1.95F0.04O0.01)

 



diopside marblediopside marble

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

sample: FKM-308
locality: The locality was given as “East Transbaikalia, Russia”, but the sample is more likely from one of the better known occurrences for blue diopside in the Prebaikalia (Pribaikal’e) region to the northwest, such as the Yoko-Dovyrensky Massif ~100 km N. of Lake Baikal.
rock type: test.
major mineralogy: The specimen was acquired for blue diopside (labeled as “violan”), although violan (sensu stricto: purple Mn3+-enriched omphacitic diopside) has not been previously reported from Russia.

 



fuchsite kyanite staurolite schistfuchsite kyanite staurolite schist

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

sample: FKM-309
locality: Kola Peninsula, Murmansk Oblast, Russia.
rock type: test.
major mineralogy: The specimen was acquired for fuchsite, staurolite and garnet.

 



svanbergitesvanbergite

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

sample: FKM-310
locality: Champion Mine, White Mountain Peak, White Mts, Mono Co., CA, USA.
rock type: test.
major mineralogy: The specimen was acquired for svanbergite.

 



thulitethulite

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

sample: FKM-311
locality: Snillfjord, Krokstadøra, Trondheim, Sør-Trondelag, Norway.
rock type: test.
major mineralogy: The specimen was acquired for thulite.

 



fuchsite schistfuchsite schist

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

sample: FKM-312
locality: MQ Granite AS quarry, Gaskkabeaivári, Kautokeino, Finnmark, Norway.
rock type: test (Masi Quartzite).
major mineralogy: The specimen was acquired for “fuchsite”.
accompanying videos: Short videos featuring the mineral associations and optical properties of the Cr-bearing muscovite (“fuchsite”) in this thin section offer a more detailed look at this sample.

 



haüyne phonolitehaüyne phonolite

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

sample: FKM-313
locality: In den Dellen quarries, Niedermendig, Mendig, Mayen-Koblenz, Rhineland-Palatinate, Germany.
rock type: test.
major mineralogy: The specimen was acquired for haüyne.
accompanying videos: Short videos featuring the mineral associations and optical properties of the haüyne in this thin section offer a more detailed look at this sample.

mineral representative mineral compositions in FKM-313
magnetite analysis pending
apatite analysis pending
titanite analysis pending
clinopyroxene analysis pending
sanidine analysis pending
plagioclase analysis pending
haüyne (Na5.70K0.30)[Si6.01Al5.96Fe3+0.03O24] . (Ca1.57Na0.15Sr0.01)([SO4]2-1.47?[HSO4]1-?0.18?Cl0.17[S3?]2-0.01?F0.01)
K-rich feldspathoid analysis pending

 



spinel pargasite marblespinel pargasite marble

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

sample: FKM-314
locality: Ali Abad, Hunza Valley, Gilgit District, Gilgit-Baltistan, Pakistan.
rock type: test.
major mineralogy: The specimen was acquired for pargasite.

 



rinkite syeniterinkite syenite

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

rinkite in thin section under UV light

under shortwave ultraviolet [SWUV] illumination

 
sample: FKM-315 (billet courtesy of R. Mielke [Cobalt, Ontario]; sample 628)
locality: Kipawa alkaline complex, Les Lacs-du-Témiscamingue, Abitibi-Témiscamingue, Québec, Canada.
rock type: metamorphosed alkali syenite.
major mineralogy: The specimen was acquired for rinkite-(Y), omphacite, fluoro-richterite and albite. Several additional samples from the Kipawa complex are featured as part of this collection and represent a variety of diverse mineral assemblages from the greater metamorphosed body; these include samples FKM-27, FKM-64, FKM-65 and FKM-211.

accompanying videos: Short videos featuring the mineral associations and optical properties of the fluorite, hiortdahlite, omphacite/aegirine-augite and microcline in this thin section offer a more detailed look at this sample.

mineral representative mineral compositions in FKM-315
fluorite not analyzed
hiortdahlite pending
mosandrite-(Ce) pending
omphacite-dominant cpx ss
(main central zone)
(Ca0.72Na0.27Mn2+0.01)(Mg0.63Al0.14Fe3+0.12Fe2+0.09Zr0.01)[Si1.99Al0.01O6]
aegirine-augite-dominant cpx ss
(near rim; most [Ca+Mg]-rich)
(Ca0.68Na0.31Mn2+0.01)(Mg0.55Fe3+0.20Fe2+0.12Al0.11Mn2+0.01Zr0.01)[Si1.99Al0.01O6]
aegirine-augite-dominant cpx ss
(patchy; most [Na+Fe]-rich)
(Ca0.51Na0.48)(Mg0.38Fe3+0.33Fe2+0.16Al0.08Mn2+0.02Zr0.02Ti0.01)[Si2.00O6]
microcline (K0.89Na0.09Ba0.02)[Si2.98Al1.01O8]
albite Na1.00[Si3.00Al0.99O8]

 



shuiskite and uvarovite in chromiteshuiskite and uvarovite in chromite

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

sample: FKM-316 (billet from the Univ. Arizona mineralogy collection; sample was orphaned and subsequently dis-used)
locality: this unlabeled sample is almost certainly from the classic Saranovskii mine, Saranovskaya village, Permskaya Oblast’ (middle Ural Mtns. region), Russia locality, or from one of the lesser-known adjacent localities in the same ore field.
rock type: hydrothermally altered and metamorphosed chromitite.
major mineralogy: The specimen was acquired for uvarovite and a Cr-rich pumpellyite group mineral. The garnet is bright green in PPL and anomalously birefringent under XP (with sector zones showing up to 1st order gray to white birefringence [tinted green from the underlying mineral color]), predominately Cr-rich grossular in composition but grading to Al-rich uvarovite along the rims. The pumpellyite group mineral is patchy zoned and ranges from 8.8 wt% to 20.4 wt% Cr2O3 (with ~14.0 wt% Cr2O3 in the main mod-z portions). These Cr concentrations suggest both Cr-rich pumpellyite-(Mg) sensu stricto and the YCr-dominant pumpellyite group mineral shuiskite (UPDATE: renamed in 2020 to shuiskite-(Mg), per pumpellyite group nomenclature recommendations, due to the 2019 discovery of [XCr-dominant]+[YCr-dominant] shuiskite-(Cr), also from the Saranovskii mine) are present. Unfortunately, as with the Cr-bearing tourmalines, Cr in pumpellyite group minerals may be partitioned between two different sites: the X-site (typically dominated by Mg, Fe2+, Fe3+, Mn2+ or Al; the major cation in this site is denoted in the mineral name by a suffix), and the Y-site (where the dominant cation defines the root name of the subgroup: YAl defines the pumpellyite sensu stricto subgroup and YCr defines the formerly lone-member shuiskite subgroup [and where YFe3+, YMn3+ and YV3+ define other, less well-known subgroups]); hence, knowledge of the precise distribution of Cr (and indeed other elements as well) between the X-site and Y-site is necessary to correctly identify the proper subgroup. Again also as with the Cr-bearing tourmalines, the distribution of Cr between the X-site and the Y-sites in pumpellyite group minerals cannot be determined unequivocally just by chemical analysis alone, and the correct cation assignment nominally requires an X-ray structural refinement. However, several researchers have attempted to ascertain if an underlying pattern to the Cr site occupancy can be elucidated that would further our understanding of how Cr is accommodated in pumpellyite group minerals. Most recent of these is Lykova et al., 2018 [← subscription required], which benefits from additional compiled data from several earlier structural refinements complementing their own data. Their conclusion is that for relatively low Cr concentrations, Cr prefers X-site occupancy, but at fairly high Cr concentrations, Cr increasingly begins to favor the Y-site. Using data presented in Lykova et al., 2018, the distribution of Cr between the X-site and Y-site of the three analyses presented below were estimated. The results are consistent with results from Lykova et al., 2018 for analyses of similar total (X+Y)Cr apfu (and note that this comparison is only to other samples from the Saranovskaya ore field, thus minimizing the possibility that any unrecognized Cr-partitioning effects due to differences in the regional P-T-X conditions at other localities might skew the observed relationship), and also appear to show some compelling trends in other elements. The garnet and pumpellyite, along with associated zoned Cr-rich clinochlore, occur as thin veinlets traversing the variably altered cumulate magnesiochromite. The alteration, most pervasive closest to the silicate veinlets but also prevalent along magnesiochromite grain edges elsewhere in the sample, shows marked enrichment in Fe (and normalizes as chromite). Interstitial to the magnesiochromite/chromite grains is additional Cr-rich clinochlore and sparse F-rich hydroxylapatite. Two other samples from the Saranovskii mine are also represented among the FKM thin section collection, but differ slightly in silicate alteration mineralogy from sample FKM-316; sample FKM-149 shares the uvarovite and clinochlore but lacks pumpellyite, whereas sample FKM-215 contains amesite rather than clinochlore, but also neither garnet nor pumpellyite.

mineral representative mineral compositions in FKM-316
magnesiochromite-dominant
spinel group ss
(Mg0.61Fe2+0.38Ni0.01)(Cr1.16Al0.67Fe3+0.12Fe2+0.02Ti0.01)O4
chromite-dominant
spinel group ss
(Fe2+0.83Mg0.14Mn2+0.02Si0.01)(Cr1.68Al0.22Fe3+0.07Fe2+0.02Ti0.01)O4
hydroxylapatite (Ca5.00Sr0.01Na0.01)[P0.99Si0.003S0.003O4]3([OH]0.55F0.44Cl0.01)
uvarovite-dominant garnet ss (rim) Ca3.00(Cr1.18Al0.74Ti0.04Fe3+0.02V0.01)[Si1.00O4]3
grossular-dominant garnet ss (main) Ca3.01(Al1.00Cr0.91Ti0.04Fe3+0.02V0.01)[Si0.98Al0.017O4]3
pumpellyite-(Mg)-dominant
pumpellyite group ss
(small patches; most Al-rich)
(Ca1.96Na0.01Mg0.01)(Mg0.48Cr0.26Al0.25V0.01)(Al1.69Cr0.31)
[Si1.00O4][Si2.00O6.52(OH)0.48](OH)1.00([OH]1.99F0.01)
pumpellyite-(Mg)-dominant
pumpellyite group ss
(main; most Cr-rich)
(Ca1.96Na0.01)(Mg0.40Cr0.31Al0.27V0.01Ti0.01)(Al1.38Cr0.62)
[Si1.00O4][Si2.02O6.63(OH)0.37](OH)1.00([OH]1.99F0.01)
shuiskite-(Mg)-dominant
pumpellyite group ss (patchy)
(Ca1.96Na0.01)(Mg0.37Cr0.35Al0.26Fe2+0.01Ti0.01)(Cr1.04Al0.96)
[Si1.00O4][Si2.02O6.67(OH)0.33](OH)1.00([OH]1.99F0.01)
clinochlore (most Cr-rich) (Mg4.21Al0.82Cr0.71FeT0.07Ni0.020.17)[Si2.75Al1.25O10](OH)8.00
clinochlore (most Mg-rich) (Mg4.68Al1.02Cr0.15FeT0.04Ni0.030.08)[Si2.95Al1.04O10](OH)8.00

accompanying videos: Short videos featuring the mineral associations and optical properties of the Cr-rich pumpellyite-(Mg)/shuiskite-(Mg) 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)
shuiskite-(Mg)/
pumpellyite-(Mg)

PPL: lavender/pale green pleochroism, high relief;
XP: up to 2nd order green δ;
with uvarovite

 



Franklin minerals in thin sectionFranklin minerals in thin section

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

Franklin minerals in thin section under UV light

under shortwave ultraviolet [SWUV] illumination

 
sample: FKM-317 (billet courtesy of M. Baum [Rockaway, New Jersey]; referred to in the sample’s accompanying paperwork as both #461 and mineral “E” [see below])
locality: Franklin Mine, Franklin Mining District, Sussex Co., NJ, USA.
rock type: test.
major mineralogy: this sample is a portion of a larger “reserve” specimen believed to contain, in part, a hydrous zinc-rich arsenate referred to on mindat.org as mineral “E”, and in Dunn et al., 1982 as “a second phase related to chlorophoenicite” and also as the museum catalog number NMNH 14909 of the specimen they originally examined. This material is purported to be a Zn-dominant end-member in the chlorophoenicite family, i.e. (Zn,Mg,Mn2+)3Zn2[AsO4](OH,O)6. Numerous samples from the Franklin and Sterling Hill areas are represented among this collection; however, the only other arsenate-bearing sample is FKM-304, a kraisslite-bearing sample from Sterling Hill.

 



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

sample: FKM-318
locality: The original label listed only “Ural Mountains, Russia”, but the specimen is consistent with the material from the “pit 298” diggings or one of the adjacent diggings near the boundary of the Ilmen Nature Preserve in Chelyabinsk Oblast, Russia.
rock type: desilicified syenite pegmatite.
major mineralogy: The specimen was acquired for corundum, biotite and K-feldspar. Blocky crystals of zircon, xenotime or monazite were observed associated with the biotite clots, and members of the columbite/samarskite groups are reported from the locality.
(left: unpolarized light; right: under crossed polars)

 



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

sample: FKM-319 (dealer sample number 2795)
locality: Vasin-Myl’k Mt, Voron’i Tundry, Murmansk Oblast, Russia.
rock type: phosphate-rich zone in a LCT-type granite pegmatite.
major mineralogy: The specimen was acquired for fairfieldite.

 



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

sample: FKM-320 (dealer sample number 7101)
locality: Koashva Mt, Khibiny Massif, Murmansk Oblast, Russia.
rock type: agpaitic nepheline syenite.
major mineralogy: The specimen was acquired for paraumbite and eudialyte.

 



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

sample: FKM-321 (dealer sample number 7100)
locality: Hatrurim Formation, Negev, Israel.
rock type: sanidinite facies pyrometamorphic phosphatic marble.
major mineralogy: The specimen was acquired for kalsilite.

 



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

sample: FKM-322 (dealer sample number 4447)
locality: Izumrudnye Kopi area, Malyshevo, Yekaterinburg, Sverdlovsk Oblast, Russia. Margarite, specifically beryllian margarite, is explicitly noted on mindat as present in the Malyshevskaya pit, but is likely also present in other emerald occurrences within the ~25 km by ~2 km belt.
rock type: test.
major mineralogy: The specimen was acquired for margarite (possibly beryllian margarite).
accompanying videos: Short videos featuring the mineral associations and optical properties of the margarite 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)
margarite
PPL: near colorless, moderate relief;
XP: up to 1st order purple δ;

 



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

sample: FKM-323 (dealer sample number 2694)
locality: Rasvumchorr Mt, Khibiny Massif, Murmansk Oblast, Russia.
rock type: agpaitic nepheline syenite.
major mineralogy: The specimen was acquired for delhayelite.

 



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

under shortwave ultraviolet [SWUV] illumination

 
sample: FKM-324 (dealer sample number 4294)
locality: Jakobsberg Mine, Jakobsberg ore field, Nordmark district, Filipstad, Värmland, Sweden.
rock type: Although not associated with a causative intrusion, and indeed presumably formed by a completely different process, this mineralization style has been commonly referred to as a “Mn skarn”. A better term for this and related occurrences may be “calcareous Mn-metasomatite”. The original Fe and Mn were likely derived from exhalative hydrothermal processes, perhaps akin to those of modern seafloor “black smokers”. While enrichments of some of the associated elements such as As, Sb, Ba and Pb may have been contemporaneous, others such as Be and B were likely introduced later. Subsequent high-grade metamorphism (perhaps accompanied by additional metasomatism) facilitated the redistribution of elements into the diverse and unusual mineral assemblages we observe today.
major mineralogy: The specimen was acquired for ganomalite, Mn-bearing phlogopite and calcite.
accompanying videos: Short videos featuring the mineral associations and optical properties of the ganomalite 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)
ganomalite
PPL: pale gray, very high relief;
XP: up to 2nd order yellow δ;
with phlogopite, calcite and garnet(?)

 



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

sample: FKM-325 (dealer sample number 3497)
locality: Popigai impact crater, Krasnoyarsk Krai, Russia.
rock type: test.
major mineralogy: The specimen was acquired for “maskelynite”, an impact glass of approximately plagioclase composition, and also if I’m lucky, possibly impact diamonds.

 



next page (samples FKM-326 to FKM-350)

previous page (samples FKM-276 to FKM-300)