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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left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-376 (two thin sections cut from the same billet are shown here)
locality: sub-locality #2, at Mautia Hill, Kongwa, Kongwa District, Dodoma Region, Tanzania.
rock type: whiteschist-associated UHP metamorphic rock.
major mineralogy: The specimen was acquired for magnesio-fluoro-hornblende (pink in hand sample) and anthophyllite (yellow in hand-sample).
upper left image: plane-polarized light (E-W); upper right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-377
locality: Fuka mine, Fuka, Bicchi-cho, Takahashi City, Okayama prefecture, Japan.
rock type: test.
major mineralogy: The specimen was acquired for henmilite and olshanskyite.
accompanying videos: Short videos featuring the mineral associations and optical properties of the henmilite 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) |
|---|---|---|---|---|
| henmilite PPL: medium indigo-violet/medium-pale lilac/pale pink pleochroism, moderate relief; XP: up to 2nd order green δ; with undifferentiated Ca borates |
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left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-378
locality: eclogite outcrops near Silberbach, Hof district, Bavaria, Germany.
rock type: eclogite.
major mineralogy: The specimen was acquired for garnet and Cr-bearing omphacite.
left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-379
locality: Bonnet Island, Georgian Bay, Parry Sound district, Ontario, Canada.
rock type: felsic granulite.
major mineralogy: The specimen was acquired for menzerite-(Y) (type locality), which forms scattered cores and inclusions in Y-rich almandine. Also perhaps present are K-feldspar, oligoclase, ferrosilite, augite and allanite.
left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-380
locality: Utö mines, Utö, Stockholm county, Sweden.
rock type: blackwall between LCT pegmatite and host rocks.
major mineralogy: The specimen was acquired for holmquistite (type locality).
accompanying videos: Short videos featuring the mineral associations and optical properties of the holmquistite 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) |
|---|---|---|---|---|
| holmquistite PPL: pale yellow-green/medium violet pleochroism, high relief; XP: up to 1st order purple δ; with biotite and quartz |
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left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-381
locality: Tawmaw area, Hpakant-Tawmaw jade tract, Kachin state, Burma.
rock type: jadeitite.
major mineralogy: The specimen was acquired for kosmochlor.
accompanying videos: Short videos featuring the mineral associations and optical properties of the Cr-rich jadeite and Cr-rich eckermannite 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) |
|---|---|---|---|---|
| Cr-rich jadeite PPL: near colorless/pale green/medium bright greenish-yellow pleochroism, moderate-high relief; XP: up to 1st order orange δ, with anomalous blue and brown overtones in low birefringence sections; with Cr-rich eckermannite and kosmochlor |
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| Cr-rich eckermannite PPL: near colorless/pale green pleochroism, moderate relief; XP: up to 2nd order blue δ, with anomalous blue and brown overtones in low birefringence sections; with Cr-rich jadeite and kosmochlor |
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upper left image: plane-polarized light (E-W); upper right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-382
locality: Durham Ranch, near Wright, Campbell Co., WY, USA.
rock type: paralava.
major mineralogy: The specimen was acquired for esseneite and gehlenite.
accompanying videos: Short videos featuring the mineral associations and optical properties of the esseneite 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) |
|---|---|---|---|---|
| esseneite PPL: weak medium greenish-yellow/dark greenish-orange pleochroism, high relief; XP: up to 2nd order yellow δ, although body color of mineral largely masks birefringence; with plagioclase feldspar and glass |
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left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-383
locality: Durham Ranch, near Wright, Campbell Co., WY, USA.
rock type: paralava.
major mineralogy: The specimen was acquired for srebrodolskite and gehlenite.
accompanying videos: Short videos featuring the mineral associations and optical properties of the srebrodolskite and ye’elimite 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) |
|---|---|---|---|---|
| srebrodolskite PPL: weak deep red-orange/deep brownish-red pleochroism, high relief; XP: birefringence masked by body color of mineral; with gehlenite and larnite |
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| ye’elimite PPL: colorless, low relief; XP: isotropic with srebrodolskite, gehlenite and larnite |
isotropic | |||
left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-384
locality: Durham Ranch, near Wright, Campbell Co., WY, USA.
rock type: paralava.
major mineralogy: The specimen was acquired for alumoåkermanite.
accompanying videos: Short videos featuring the mineral associations and optical properties of the varying compositions of the melilite 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) |
|---|---|---|---|---|
| “blue melilite” PPL: near colorless/medium greenish-blue pleochroism, moderate relief; XP: up to 1st order yellow δ, but with blue anomalous overtones and also partially obscured by mineral body color; (analyses for composition and associated minerals are pending) |
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| “yellow melilite” PPL: core-to-rim zoned near colorless/pale yellow to very pale yellow/dark yellow pleochroism, moderate relief; XP: core-to-rim zoned up to 1st order yellow δ but with strong anomalous blue overtones (core), and up to 2nd order green-yellow δ (outermost rim); (analyses for composition and associated minerals are pending) |
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left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-385
locality: Seixoso Mine, near Lixa, Porto, Portugal.
rock type: test.
major mineralogy: The specimen was acquired for zinconigerite-2N1S, although only the Fe-dominant ferronigerite-2N1S end-member is currently reported for the locality.
accompanying videos: Short videos featuring the mineral associations and optical properties of the vivianite 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) |
|---|---|---|---|---|
| vivianite PPL: deep indigo blue/light greenish-yellow pleochroism, moderate-high relief; XP: bright high-order δ partially masked by mineral color; with quartz, muscovite, additional Fe-phosphates and zinconigerite-2N1S |
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left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-386
locality: lower level of the Bor pit, Dal’negorsk, Primorsky Krai, Russia.
rock type: test.
major mineralogy: The specimen was acquired for dalnegorskite (type locality) and hedenbergite.
accompanying videos: Short videos featuring the mineral associations and optical properties of the datolite 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) |
|---|---|---|---|---|
| datolite PPL: near colorless, low-moderate relief; XP: up to 3rd order green δ; with Mn-rich ferrobustamite and hedenbergite |
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left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-387
locality: Långban, Filipstad, Värmland, Sweden.
rock type: test.
major mineralogy: The specimen was acquired for mangani-pargasite and hausmannite.
accompanying videos: Short videos featuring the mineral associations and optical properties of the mangani-pargasite 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) |
|---|---|---|---|---|
| mangani-pargasite PPL: near colorless/medium peach-tan/medium orange-peach pleochroism, moderate-high relief; XP: up to 2nd order blue-green δ; with hausmannite and phlogopite |
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left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-388
locality: Xianghualing Mine, Xianghualing Sn-polymetallic ore field, Linwu Co., Chenzhou, Hunan, China.
rock type: phlogopite-rich greisen-like skarn developed in metamorphosed limestone intruded by granite.
major mineralogy: The specimen was acquired for hsianghualite, fluorite, and possibly additional rarer Be and Li minerals.
accompanying videos: Short videos featuring the mineral associations and optical properties of the hsianghualite 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) |
|---|---|---|---|---|
| hsianghualite PPL: colorless, moderate-low relief; XP: isotropic with phlogopite and fluorite |
isotropic | |||
left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-389
locality: Commercial quarry, Crestmore quarries area, Crestmore, Riverside Co., CA, USA..
rock type: test.
major mineralogy: The specimen was acquired for clintonite.
accompanying videos: Short videos featuring the mineral associations and optical properties of the clintonite 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) |
|---|---|---|---|---|
| clintonite PPL: very weak very pale brownish-yellow/near colorless pleochroism, moderate-high relief; XP: up to 1st order yellow-orange δ; with monticellite, calcite and garnet |
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left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-390
locality: North Thunderbird mine, Mesabi range, St. Louis county, MN, USA..
rock type: test.
major mineralogy: The specimen was acquired for minnesotaite and greenalite.
left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-391
locality: “Liebenbergite slag dump”, near Agios Konstantinos, greater Lavrion area, East Attica, Attica, Greece..
rock type: test.
major mineralogy: The specimen was acquired for schäferite.
left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-392
locality: “Liebenbergite slag dump”, near Agios Konstantinos, greater Lavrion area, East Attica, Attica, Greece..
rock type: test.
major mineralogy: The specimen was acquired for liebenbergite, trevorite and schäferite.
accompanying videos: Short videos featuring the mineral associations and optical properties of the schäferite and liebenbergite-forsterite solid-solution 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) |
|---|---|---|---|---|
| schäferite PPL: brownish-orange, high relief; XP: isotropic, but with patchy areas of anomalous anisotropy; with plagioclase |
isotropic | |||
| liebenbergite-forsterite ss PPL: zoned pale green/medium green to medium green/deep brownish-green pleochroism, high relief; XP: high order (4th?) pinkish(?), but difficult to discern/ascertain; with trevorite-dominant spinel (opaque); colorless is epoxy |
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upper left image: plane-polarized light (E-W); upper right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-393
locality: This is apparently a relatively new lapidary material marketed as “fireworks stone” being currently sold largely out of China (although Chinese-sold rocks, particularly lapidary materials, could be sourced from anywhere in the world); the specific locality is currently not reported (it may be Greenland… see below).
rock type: Based on the original hand sample evaluation, the rock was first thought to be an igneous syenite of some type. However, subsequent examination of the thin section indicates that the rock is actually a metamorphic orthoamphibolite resembling the lapidary material “nuummite”; for example, Franz et al., 2016 describe an orthoamphibole with blue/violet iridescence from a “nuummite” of comparable assemblage from Greenland.
major mineralogy: Based on the original hand sample evaluation, the rock was acquired for the presumed assemblage of a blue-black “arfvedsonite root-name” sodic amphibole (UPDATE: now shown to be an orthoamphibole, either anthophyllite and/or gedrite), a red eudialyte group mineral (UPDATE: now believed to be almandine garnet, although curiously no garnet was intersected in the thin section), black prismatic aegirine (UPDATE: likely mistaken for the staurolite present) and pyrite (UPDATE: indeed present and abundant, although now also shown to be accompanied by subordinate but significant pyrrhotite and chalcopyrite). The amphibole forms large attractive sprays with a bright blue labradorite-like schiller, and this schiller is even seen in the thin section when viewed by hand; however, the effect is not observed under the microscope. Abundant sprays of chlorite, and also areas of intergrown cordierite and quartz (especially difficult to differentiate in this sample) are present.
left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-394 (billet courtesy of Yoshiya Ohki, Nippon Chigaku Kenkyu-kai [Kyoto])
locality: Yamanobo, Itoigawa City, Niigata Prefecture, Japan. Note: the Yamanobo outcrop is now preserved as a natural monument and is included within the Itoigawa UNESCO Global GeoPark, and collecting there is prohibited. The excess sample from which this thin section was prepared was kindly donated by Yoshiya Ohki, who co-authored a scientific study on the mineral chemistry of the locality and received special permission to collect there.
rock type: blueschist-facies jadeitic eckermannite-amphibolite.
major mineralogy: The specimen was acquired for kosmochlor, Cr-enriched eckermannite and possibly a Cr-dominant (VICr > VIAl) eckermannite-group amphibole; the petrology and chemistry of these uncommonly Cr-rich biopyriboles from Yamanobo are detailed in Takasu et al., 2022.
left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-395 (billet courtesy of Yoshiya Ohki, Nippon Chigaku Kenkyu-kai [Kyoto])
locality: Yamanobo, Itoigawa City, Niigata Prefecture, Japan. Note: the Yamanobo outcrop is now preserved as a natural monument and is included within the Itoigawa UNESCO Global GeoPark, and collecting there is prohibited. The excess sample from which this thin section was prepared was kindly donated by Yoshiya Ohki, who co-authored a scientific study on the mineral chemistry of the locality and received special permission to collect there.
rock type: blueschist-facies jadeitic eckermannite-amphibolite.
major mineralogy: The specimen was acquired for kosmochlor and Cr-enriched eckermannite; the petrology and chemistry of these uncommonly Cr-rich biopyriboles from Yamanobo are detailed in Takasu et al., 2022.
left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-396 (billet courtesy of Yoshiya Ohki, Nippon Chigaku Kenkyu-kai [Kyoto])
locality: Ohmi river (Ohmi-gawa), Ōmi, Itoigawa City, Niigata Prefecture, Japan.
rock type: jadeitite.
major mineralogy: The specimen was acquired for itoigawaite and jadeite.
accompanying videos: Short videos featuring the mineral associations and optical properties of the varying compositions of the itoigawaite and pectolite 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) |
|---|---|---|---|---|
| itoigawaite (likely with pectolite, jadeite and prehnite) | video pending | video pending | video pending | |
| pectolite PPL: colorless, moderate-high relief; XP: up to 2nd order yellow δ; with jadeite, prehnite and itoigawaite |
video pending | |||
left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-397 (billet courtesy of Yoshiya Ohki, Nippon Chigaku Kenkyu-kai [Kyoto])
locality: Ohmi river (Ohmi-gawa), Ōmi, Itoigawa City, Niigata Prefecture, Japan.
rock type: albitite.
major mineralogy: The specimen was acquired for ohmilite, magnesio-riebeckite and albite.
left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-398 (billet courtesy of Yoshiya Ohki, Nippon Chigaku Kenkyu-kai [Kyoto])
locality: Ohmi river (Ohmi-gawa), Ōmi, Itoigawa City, Niigata Prefecture, Japan.
rock type: albitite.
major mineralogy: The specimen was acquired for strontio-orthojoaquinite, benitoite, magnesio-riebeckite, sepiolite and albite.
left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-399 (billet courtesy of Yoshiya Ohki, Nippon Chigaku Kenkyu-kai [Kyoto])
locality: Iwagi Island, Ochi District, Ehime Prefecture, Japan.
rock type: albitite.
major mineralogy: The specimen was acquired for sugilite, katayamalite and albite.
accompanying videos: Short videos featuring the mineral associations and optical properties of the varying compositions of the katayamalite, sugilite, aegirine-augite and murakamiite-pectolite ss 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) |
|---|---|---|---|---|
| katayamalite PPL: near colorless, moderate-high relief; XP: up to 1st order gray δ, but masked by anomalous deep blue/brown overtones; with albite, murakamiite-pectolite ss and sugilite |
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| sugilite PPL: colorless, moderate relief; XP: up to 1st order dark gray δ; with albite, murakamiite-pectolite ss and aegirine-augite |
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| aegirine-augite PPL: medium/dark green pleochroism, high relief; XP: up to 2nd order orange δ, but partially obscured by mineral body color; with albite, quartz, murakamiite-pectolite ss and sugilite |
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| murakamiite-pectolite ss PPL: near colorless, moderate-high relief; XP: up to 2nd order pink δ; with albite |
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left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image
sample: FKM-400 (dealer sample number 8731)
locality: N’Chwaning I Mine, Kuruman, Kalahari manganese field, Northern Cape, South Africa.
rock type: test.
major mineralogy: The specimen was acquired for sugilite.
accompanying videos: Short videos featuring the mineral associations and optical properties of the varying compositions of the sugilite and pectolite 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) |
|---|---|---|---|---|
| sugilite PPL: pale lilac, moderate-low relief; XP: up to 1st order medium-dark gray δ; with pectolite |
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| pectolite PPL: near colorless, moderate to moderate-high relief; XP: up to 2nd order green δ; with sugilite |
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