samples FKM-176 to FKM-200

 

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-176
locality: feldspar quarry, Vysoký Kámen, Krásno, Horní Slavkov, Czech Republic.
rock type: add rock type.
major mineralogy: specimen acquired for koechilinite and powellite.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-177
locality: Høgtuva beryllium deposit, Rana, Nordland, Norway.
rock type: add rock type.
major mineralogy: specimen acquired for høgtuvaite.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-178
locality: Bjurliden, Norsjö, Västerbotten, Sweden.
rock type: add rock type.
major mineralogy: specimen acquired for gahnite. For comparison, another gahnite-bearing sample featured here (in quartz rather than admixed with sulfides) is FKM-12. Additionally, several of the Franklin, NJ samples show a somewhat atypical orange to yellow gahnite (e.g. FKM-45 and FKM-48).
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-179
locality: Crestmore quarries, Crestmore, Riverside Co., CA, USA.
rock type: high-grade monticellite marble. Contact aureole (high-T low-P; sanidinite(?) facies) metamorphosed siliceous carbonate, with additional metasomatic contribution from the causative intrusion.
major mineralogy: Sample is predominately calcite (pale blue in hand sample) with abundant mm-sized porphyroblasts of monticellite and a P-bearing hydroxylellestadite (incorrectly identified on the dealer label as hydroxylapatite; P-rich ellestadite from Crestmore was formerly known as “wilkeite” and was originally thought to be a distinct species). Small scattered garnet crystals occur both as inclusions in monticellite and as discrete grains in the calcite; some are variably and irregularly zoned, whereas others are nearly homogeneous. Cr, Sc, Zr and Y are variably-enriched in the garnet. Minor gypsum is present (likely secondary… occurs along a weathered surface), and sparse tiny chalcocite is scattered within the calcite. For comparison, an essentially identical monticellite-bearing sample featured here, also from Crestmore, is FKM-10.
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-179
hydroxylellestadite (Ca4.98Na0.01)[Si1.20S1.15P0.63V0.01O12]([OH]0.72F0.16Cl0.12)
monticellite Ca1.00(Mg0.90Fe2+0.08)[Si1.01O4]
grossular-rich garnet ss (most Al+Zr-rich) (Ca2.98Mg0.02)(Al0.94Fe3+0.70Cr0.18Ti0.08Sc0.03Zr0.03Mg0.03)[Si2.90Al0.10O12]
andradite-rich garnet ss (most Cr+Sc-rich) (Ca2.90Mg0.06Y0.02)(Fe3+0.74Al0.68Cr0.46Sc0.06Ti0.05Zr0.01)[Si2.90Al0.10O12]
andradite-rich garnet ss (most Fe-rich) Ca3.00(Fe3+1.94Fe2+0.02Mg0.01)[Si3.02O12]

 



sample: FKM-180
locality: Kangerdluarsuk Fjord, Ilímaussaq complex, Narsaq, Kujalleq, Greenland.
rock type: add rock type.
major mineralogy: specimen acquired for narsarsukite.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-181
locality: Kangerdluarsuk Fjord, Ilímaussaq complex, Narsaq, Kujalleq, Greenland.
rock type: add rock type.
major mineralogy: specimen acquired for naujakasite.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-182
locality: Stollberg ore field (possibly the Stollberg mine itself), near Ludvika, Dalarna, Sweden.
rock type: high grade tephroite-hematite-rhodochrosite metasomatite. Some might call this sample a “skarn”, but I prefer to use that term specifically for a calc-silicate rock derived from metasomatism by an adjacent de-volatilizing crystallizing magma. In contrast, this rock isn’t quite “calc”, per se (with Mn > Ca), and also it may likely be a metamorphosed and metasomatized Mn-Fe exhalite with perhaps only an indirect relationship to magmatism (for example, as a heat source to drive hydrothermal fluid circulation).
major mineralogy: The rock is composed of roughly equal parts carbonate, oxide, and silicate. Small quantities of sulfides (pyrrhotite, chalcopyrite, galena and sphalerite) and fluorapatite are also present. The oxide is hematite with a small Mn component. The carbonate occurs as three distinct phases: a coarsely crystalline high-Ca rhodochrosite (which appears as the nearly colorless material in the unpolarized light scanned image) and an intimate mixture of kutnohorite and high-(Mg+Fe) rhodochrosite (these latter two carbonates are finer-grained and slightly more grayish-colored in the unpolarized light scanned image). The abundant “shattered” material in the images is “knebelite” (= a mixed Mg+Fe-rich Mn-dominant olivine [tephroite]). This material is similar to that in FKM-48 but is Fe2+ > Mg and is also Zn-free. As discussed in greater detail with respect to the tephroite in FKM-48, in this case as well the Mn2+ content is only roughly 1 apfu, so it is possible there is significant ordering of Mn2+ into the slightly larger M2 site and Mg+Fe into the slightly smaller M1 site. If this is the case, the “knebelite” in this sample, as with the material in FKM-48, may be a new ordered olivine rather than tephroite sensu strictu. The light brown material in the scanned image is a hydrous Mn-Mg-Fe silicate of varying Mn and Mg content and is a bit challenging to identify due to its fine-grained nature. Based on the optical properties of slightly coarser zones and the Si=4 normalizations, the material is most likely an Mn-rich member of the serpentine family (=caryopilite). Other less likely possibilities include a member of the chlorite family (=gonyerite) or pyrosmalite-(Mn). All three species are prevalent in many of the central Sweden Mn deposits.
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-182
pyrrhotite Fe0.88S1.00
chalcopyrite Cu1.00Fe1.00S2.00
hematite (Fe3+1.94Mn3+0.04Al0.02)O3
rhodochrosite (most Mg+Fe-rich) (Mn2+0.49Mg0.24Fe2+0.20Ca0.07)[CO3]
rhodochrosite (most Ca-rich) (Mn2+0.45Ca0.28Mg0.19Fe2+0.08)[CO3]
kutnohorite (Ca0.84Mn2+0.16)(Mn2+0.56Mg0.34Fe2+0.10)[CO3]2
fluorapatite (Ca4.90Mn2+0.07Fe2+0.02)[P3.00O12](F0.86[OH]0.11Cl0.03)
“MnFe2+[SiO4]” olivine
(most Mn-rich; historically tephroite)
Mn2+1.00(Fe2+0.66Mn2+0.25Mg0.08Fe3+0.01)[Si0.99Fe3+0.01O4]
“MnFe2+[SiO4]” olivine
(most Mg-rich; historically tephroite)
(Mn2+0.92Mg0.08)(Fe2+0.72Mg0.27Fe3+0.01)[Si0.99Fe3+0.01O4]
caryopilite? (Mn2+2.28Mg1.50Fe2+~0.94Fe3+~0.85Al0.010.43)
[Si4.00O10]([OH]7.97Cl0.03)
“Mg-caryopilite”? Ca0.01(Mg1.87Mn2+1.63Fe3+~1.49Fe2+~0.14Al0.070.79)
[Si4.00O10]([OH]7.97F0.02Cl0.01)

 



sample: FKM-183
locality: Fuka mine, Fuka, Bicchi-cho, Takahashi City, Okayama prefecture, Japan.
rock type: add rock type.
major mineralogy: specimen acquired for hillebrandtite and spurrite.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-184
locality: Edenville, near Warwick, Orange Co., NY, USA.
rock type: warwickite-forsterite-spinel-clinohumite marble. Granulite facies meta-siliceous dolostone (the boron and fluorine may be of metasomatic origin?)
major mineralogy: The sample is a magnesian marble, but with calcite > dolomite (likely due in part to the combination of dolomite-consuming + calcite-forming reactions to produce metamorphic Mg minerals). These Mg minerals include scattered spinel and relict forsterite “cores”, the latter largely replaced by clinohumite. The normalizations of both the forsterite and clinohumite suggest slight Si deficiencies in their “T” sites; small amounts of boron (~0.28 wt% B) were added to both minerals to improve their site occupancies and analytical totals. See the discussion under sample FKM-8 for more detail about the normalization scheme used for the humite group minerals, and the rationale for estimating possible boron in humite group minerals and olivine from B-rich Franklin marble assemblages. Warwickite (with 1400 ppm Zr) is the boron phase present in this sample. The warwickite shows incipient alteration along fractures to numerous tiny ilmenite grains (too small to give a good analysis), although larger discrete masses of ilmenite are also present. Sparse zirconolite is associated with the larger ilmenite; zirconolite occurrences in marble are not widely reported, so this occurrence is notable. Some special zirconolite composition and normalization features to note: HREE were estimated by an approximate linear extrapolation of the chondrite-normalized REE plot of measured L+MREE. Mg in zirconolite was presently overlooked and has been estimated here to improve the site occupancies and overall analytical total; the actual concentration of Mg, as well as the concentrations of a few additional potentially key elements (e.g. Sc) will be verified at the next opportunity and then updated here. The zirconolite normalization is based on 4 cations. However, charge balancing to the conventional 7[O] anion content did not yield satisfactory results. This suggests that the zirconolite may be partially hydrated due to radiation damage (for example, Blatt et al., 1987 propose that non-measured water accounts for their low analytical totals in high-actinide zones of zirconolite from Malawi). To account for this possibility, the zirconolite normalization allowed up to 1[O] to be replaced with 1[OH] (hence akin to a pyrochlore composition), with concomitant flexibility in assigning an M3+/∑M ratio (M = Fe+Mn) between 0 and 1. A value of M3+/∑M = 0.5 was assumed here, yielding the estimated [OH] content shown in the composition table below. Although this approach allows an estimate of the valences of Fe and Mn, Fe and Mn were reported as FeT and MnT, respectively, to emphasize the high uncertainty in this calculation in light of the present need to estimate some element concentrations. Rounding out the thin section mineralogy is a mass of talc on one side of the sample (presumably after a pre-existing Mg silicate), and veinlets of clinochlore cutting the clinohumite/forsterite crystals. Samples FKM-8, FKM-36 and FKM-112 are also examples of Franklin marble exposures from the adjoining Orange Co., NY/Sussex Co., NJ area containing humite group minerals. Sample FKM-37, also from the Franklin marble, is another B-bearing sample [with fluoborite].
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-184
spinel (Mg0.83Fe2+0.16Zn0.01)Al1.99O4
ilmenite (Fe2+0.73Mg0.21Mn2+0.04Ti0.01Ca0.01)Ti1.00O3
zirconolite (Ca0.46Y0.14U0.14[HREE]~0.13Th0.07Nd0.03Gd0.02Ce0.01Sm0.01)(Zr0.82Ti0.16Hf~0.01Nb0.01)
(Ti1.25FeT0.44Mg~0.27MnT0.02)(O~6.52[OH]~0.48)
calcite (Ca0.97Mg0.03)[CO3]
dolomite Ca1.00(Mg0.97Fe2+0.44)[CO3]2
warwickite (Mg1.24Ti0.33Al0.19Fe2+0.13Fe3+0.10V0.01)(O0.96F0.04)[BO3]
forsterite Mg1.00(Mg0.85Fe2+0.13Fe3+0.01)[Si0.96B0.04O3.98F0.02]
clinohumite (Mg8.43Fe2+0.45Ti0.10Mn2+0.02Fe3+0.01)[Si3.82B0.18O15.82(OH)0.18](F1.10[OH]0.70O0.20)
talc (Mg2.73FeT0.220.05)[Si3.99Al0.01O10]([OH]1.86F0.13)
clinochlore (Mg4.56Al1.14FeT0.18V0.010.11)[Si2.90Al1.09O10]([OH]7.88F0.11)

 



sample: FKM-185
locality: Falotta, Tinzen, Switzerland.
rock type: add rock type.
major mineralogy: specimen acquired for tinzenite.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-186
locality: Malešov, Kuntá Hora, Czech Republic.
rock type: hornblende-biotite-anthophyllite schist. Greenschist facies metamorphosed and K-metasomatized meta-serpentinite (derived from a peridotite protolith).
major mineralogy: The rock is predominately anthophyllite with subordinate Mg-rich biotite (phlogopite) and magnesio-hornblende. Minor talc is also present. Scattered relict chromite is relatively abundant, as well as lesser amounts of a variety of chalcogenides. These include primarily pentlandite, but also rare Ni-rich cobaltite (alternatively possibly glaucodot or alloclasite), Co-rich gersdorffite, and a single lath of Co-free nickeline. The cobaltite is typically enclosed in pentlandite (and adjacent pentlandite may be slightly Co-enriched), whereas the gersdorffite and lower-Co pentlandite occur randomly in the matrix. The lone observed nickeline was growing alongside a pentlandite grain. Minor thin calcite veining is present in the sample, and sparse fluorapatite and a single tiny uraninite grain were noted. All of the silicates show some enrichment in both Cr and Ni. Note that the reported distributions of Fe2+ and Mg between the VIM and VIIIM sites in the two amphiboles are not known from structural measurements but are instead assumed based only on cation size considerations.
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-186
pentlandite (most Ni-rich) (Ni4.70Fe4.24Co0.04)S8.01
pentlandite (most Co-rich) (Ni4.63Fe4.24Co0.11)S8.03
nickeline (Ni0.96Fe0.01)(As0.98S0.02)
cobaltite? (Co0.54Ni0.37Fe0.07)As0.99S1.02
gersdorffite (Ni0.59Co0.37Fe0.06)As0.98S1.01
chromite (Fe2+0.78Mg0.17Zn0.03Mn2+0.01)(Cr1.68Al0.24Fe3+0.06)O4
calcite (Ca0.92Fe2+0.03Mn2+0.03Mg0.02)[CO3]
fluorapatite (Ca4.97Y0.01Na0.01Fe2+0.01)[P3.00O12](F0.66[OH]0.29Cl0.05)
anthophyllite 1.00(Fe2+0.99Mg0.88Ca0.08Mn2+0.04Na0.19)(Mg4.88Fe3+0.10Cr0.01Ni0.01)
[Si7.90Fe3+0.07Al0.03O22]([OH]1.95F0.05)
magnesio-hornblende (K0.010.99)(Ca1.85Fe2+0.12Na0.02Mn2+0.01)(Mg4.71Fe3+0.14Fe2+0.09Cr0.06Ni0.01)
[Si7.81Al0.14Fe3+0.04O22]([OH]1.95F0.05)
talc Na0.01(Mg2.89FeT0.10Ni0.01)[Si3.98Al0.02O10]([OH]1.95F0.05)
phlogopite (K0.85Na0.010.14)(Mg2.71FeT0.19Cr0.06Al0.02Ti0.01Ni0.01)[Si2.99Al1.01O10]([OH]1.83F0.15O0.02)

 



sample: FKM-187
locality: Dehesa, San Diego Co., CA, USA.
rock type: add rock type. Compare this sample to the similar boron-bearing advanced argillic alteration assemblage in sample FKM-61 and FKM-70.
major mineralogy: specimen acquired for dumortierite.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-188
locality: Norberg area, Västmanland, Sweden (possibly from the Johanna mine or from the Malmkärra mine).
rock type: add rock type.
major mineralogy: Sample is largely composed of dollaseite-(Ce) and tremolite, with subordinate calcite and scattered gadolinite-(Nd) [Nd here is slightly greater than Ce, which is the next most abundant REE. This may be a new species; update: as of 2016, it is an approved species]. In one area of the thin section, patchy talc is intergrown with the calcite, and rare small fluorite is also present (also associated with the calcite). Rare tiny magnetite inclusions in the dollaseite-(Ce) are also observed.
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-188
magnetite Fe2+1.00Fe3+2.00O4
“gadolinite-(Nd)” (Nd0.60Ce0.55Y0.26Sm0.17Gd0.12La0.12Pr0.10[HREE]0.06Ca0.02)
(Fe2+0.69Mg0.13Ga0.010.17)(Be1.94Si0.06)[Si1.00O4]2(O1.74[OH]0.22F0.03)
dollaseite-(Ce) (Ca0.93Y0.03[HREE]0.01Gd0.01)(Ce0.54La0.30Nd0.14Pr0.05Sm0.01)(Mg0.81Fe3+0.17)
(Al0.97Fe3+0.03)(Mg0.88Fe2+0.10Mn2+0.02)(F0.71O0.28)[Si2.00O7][Si1.01O4](OH)
tremolite (Na0.01K0.010.98)(Ca1.96Na0.04)(Mg4.73Fe2+0.20Al0.05Mn2+0.01)[Si7.98Al0.02O22]([OH]1.32F0.68)
talc (Ca0.04Na0.01)(Mg2.73FeT0.10Al0.010.16)[Si4.03O10]([OH]1.88F0.12)

 



sample: FKM-189 (two thin sections cut from the same billet are shown here)
locality: Loch Scridain area, Isle of Mull, Scotland, UK.
rock type: add rock type.
major mineralogy: specimen acquired for mullite and corundum.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-190
locality: Nippyo mine, Awano, Kanuma City, Tochigi Prefecture, Honshu Island, Japan.
rock type: add rock type.
major mineralogy: specimen acquired for proto-ferro-mangano-anthophyllite (which has since been renamed as proto-ferro-suenoite), pyroxmangite and pyrophanite.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-191
locality: Andrakaholo, Anosy region, Tuléar province, Malagasy Republic.
rock type: spinel-hibonite-corundum-anorthite granulite. The protolith was likely an argillaceous carbonate.
major mineralogy: The sample is composed primarily of near end-member anorthite. Porphyroblasts of corundum are abundant (and are loaded with several types of fluid ± solid inclusions), along with scattered large porphyroblasts of spinel and hibonite. The hibonite is patchy zoned in REE. Minor calcite and baddeleyite, rare phlogopite, and a single thorianite crystal are also present. Within one baddeleyite is also a single small crystal of zirconolite. This sample bears some similarity to FKM-205 and comes from the same vicinity in Madagascar.
(left: unpolarized light; right: under crossed polars)

mineral representative mineral compositions in FKM-191
spinel (Mg0.87Fe2+0.13)Al2.00O4
corundum Al2.00O3
hibonite (most REE-rich) (Ca0.64Ce0.18La0.12Sr0.02Nd0.01Pr0.01Th0.01)(Al10.94Mg0.61Ti0.29Fe2+0.08Fe3+0.04Si0.04)O19
hibonite (most Ti-rich) (Ca0.97Sr0.02Na0.01Ce0.01Nd0.01Th0.01)(Al10.59Ti0.62Mg0.57Fe2+0.12Si0.05Fe3+0.02)O19
zirconolite (Ca0.67Y0.09U0.09Th0.06[HREE]0.04Gd0.01Sm0.01Nd0.01Ce0.01)
Zr1.00(Ti1.41Al0.19Zr0.17Fe2+0.15Nb0.04Hf0.01V0.01)O7
fluorapatite (Ca4.97Y0.01Ce0.01Nd0.01)[P2.93Si0.04O12](F0.98[OH]0.01Cl0.01)
phlogopite (K0.89Na0.06Ba0.020.03)(Mg2.74Al0.17FeT0.05Ti0.03)[Si2.81Al1.19O10]([OH]1.10F0.84O0.07)
anorthite (Ca0.98Na0.01)[Al2.02Si1.98O8]

 



sample: FKM-192
locality: Union Carbide Mine, Wilson Springs (Potash Sulfur Springs), Garland Co., Arkansas, USA.
rock type: add rock type.
major mineralogy: specimen acquired for wollastonite (and aegirine seems present as well).
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-193
locality: Långban, Filipstad, Värmland, Sweden.
rock type: add rock type.
major mineralogy: specimen acquired for cymrite. This sample is mineralogically very similar to FKM-86, also from Långban, and also contains melanotekite and phlogopite.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-194
locality: Webing, near Abtenau, Salzburg, Austria.
rock type: add rock type.
major mineralogy: specimen acquired for crossite.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-195
locality: Sunnyside mine, Silverton, CO, USA.
rock type: add rock type.
major mineralogy: specimen acquired for pyroxmangite.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-196
locality: unspecified locality in Namibia.
rock type: cassiterite-bearing granite.
major mineralogy: specimen acquired for cassiterite.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-197
locality: southwestern Tasmania, Australia, possibly from the BHP prospect, Birches Inlet, Macquarie Harbour locality.
rock type: add rock type.
major mineralogy: specimen acquired for stichtite and serpentine.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-198
locality: Black Mountain, Greenwood, Oxford Co., Maine, USA.
rock type: add rock type.
major mineralogy: specimen acquired for elbaite and lepidolite.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-199
locality: Kaokoveld Plateau, Kunene region, Namibia.
rock type: add rock type.
major mineralogy: specimen acquired for shattuckite.
(left: unpolarized light; right: under crossed polars)

 



sample: FKM-200
locality: Red Cloud Fluorite mine, Gallinas Mts, Red Cloud District, Lincoln Co., New Mexico, USA.
rock type: add rock type.
major mineralogy: specimen acquired for bastnasite-(Ce) and fluorite.
(left: unpolarized light; right: under crossed polars)

 



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