samples FKM-401 to FKM-425

 

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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left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-401 (dealer sample number 8806)
locality: Lupikko Mine, Pitkyaranta, Pitkyarantsky District, Republic of Karelia, Russia.
rock type: test.
major mineralogy: The specimen was acquired for helvine.

accompanying videos: Short videos featuring the mineral associations and optical properties of the fluorite, ferro-pargasite, biotite and danalite 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)
fluorite
PPL: patchy colorless to deep purple In some cases as halos), moderate negative relief;
XP: isotropic;
with biotite and minor ferro-pargasite
isotropic
ferro-pargasite
PPL: blue/green/light yellow-tan pleochroism, moderate-high relief;
XP: up to 1st order orange δ (to 1st order purple δ not in this view);
with biotite
biotite
PPL: dark brown/medium brown/very pale buff pleochroism, moderate-high relief;
XP: up to low 3rd order colors, partially obscured by mineral body color;
with ferro-pargasite
danalite
PPL: light-medium brown, high relief;
XP: isotropic;
with fluorite, biotite and ferro-pargasite
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-402
locality: Moss mine, near Nordmark, Filipstad, Värmland, Sweden.
rock type: test.
major mineralogy: The specimen was acquired for synadelphite.

 



left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-403 (dealer sample number 7309)
locality: The dealer label lists the locality as “Pitkyaranta, northeastern Ladoga region, SW Karelia, Russia”. The sample is likely more specifically from the Ristiniem peninsula (approximately 3 km south of Pitkyaranta), a collecting area where high-grade banded “calciphyres” were locally mined.
rock type: high-grade magnesian marble.
major mineralogy: The specimen was acquired for norbergite; however, although some norbergite is present in the sample, the bulk of the humite-group mineral present is chondrodite.

accompanying videos: Short videos featuring the mineral associations and optical properties of the chondrodite in this thin section offer a more detailed look at this sample. Chondrodite makes up the bulk of the humite-group minerals visible in this video set, but it is not easily distinguished here from the roughly 20% present that is norbergite.

mineral PPL (lower
polar rotation)
PPL
(stage rotation)
XP
(stage rotation)
optic figure
(stage rotation)
chondrodite
PPL: zoned colorless/light-medium yellow pleochroism, moderate-high relief;
XP: up to 1st order purple δ;
with norbergite and calcite

 



left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-404
locality: Magnet Cove, Hot Spring Co., Arkansas, USA.
rock type: carbonatite.
major mineralogy: The specimen was acquired for kimzeyite garnet, magnetite, perovskite, calcite and apatite. Analyses of both garnet core and rim show little variation in chemistry, but in both cases, IVFe3+ is somewhat greater than IVAl. Hence, the garnet in this sample appears to be kerimasite rather than kimzeyite.

accompanying videos: Short videos featuring the mineral associations and optical properties of the perovskite, apatite, monticellite and kerimasite 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)
perovskite
PPL: dark brown, high relief;
XP: presumably high order birefringence, obscured by mineral body color; complexly twinned;
with apatite, magnetite and calcite
hydroxylapatite
PPL: colorless, moderate relief;
XP: up to 1st order gray δ;
with kimzeyite garnet, perovskite and calcite
monticellite
PPL: colorless, moderate relief;
XP: up to 1st order gray-white δ;
with apatite and calcite
kerimasite
PPL: medium brown, high relief;
XP: isotropic;
with perovskite, apatite and calcite
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-405
locality: Bastnäs, Riddarhyttan, Skinnskatteberg, Västmanland, Sweden.
rock type: best described as a REE metasomatite.
major mineralogy: The specimen was acquired for ferri-allanite-(Ce), actinolite and pyrite.

 



left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-406 (dealer sample number 7897)
locality: Nueva Vizcaya Mine, Burguillos del Cerro, Badajoz, Extremadura, Spain.
rock type: metasomatic Fe-oxide.
major mineralogy: The specimen was acquired for allanite-(La), although apparently allanite-(La) only makes up thin bands within zoned composite crystals of allanite-(Ce)/allanite-(La)/REE-rich epidote. Additionally, the specimen may contain diopside, K-Cl-rich calcic amphibole, magnetite and Co-bearing löllingite.

 



left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-407
locality: Rasvumchorr Mt, Khibiny Massif, Murmansk Oblast, Russia.
rock type: agpaitic nepheline syenite.
major mineralogy: The specimen was acquired for fenaksite.

accompanying videos: Short videos featuring the mineral associations and optical properties of the varying compositions of the lomonosovite, barytolamprophyllite, aenigmatite and delhayelite 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)
lomonosovite
PPL: pale orange/medium yellow-orange/dark lilac-brown pleochroism, high relief;
XP: up to high order pastel pink/green colors;
with barytolamprophyllite, delhayelite, eudialyte, K-feldspar and nepheline
barytolamprophyllite
PPL: medium-light yellow/medium orange-yellow/medium brownish-yellow pleochroism, high relief;
XP: up to 2nd order orange-yellow δ;
with aenigmatite, delhayelite, potassic-arfvedsonite, K-feldspar and nepheline
aenigmatite
PPL: dark red-brown/black (opaque) pleochroism, high relief;
XP: birefringence masked by near opacity/body color of mineral;
with aegirine, delhayelite, potassic-arfvedsonite, barytolamprophyllite and nepheline
crystals were too dark to obtain an optic figure
delhayelite
PPL: colorless, but with localized weak incipient alteration showing tan/bluish-gray pleochroism, low relief;
XP: up to 1st order dark gray δ, with anomalous brown overtones;
with aenigmatite, barytolamprophyllite and nepheline

 



left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-408 (dealer sample number 8783)
locality: Långban, Filipstad, Värmland, Sweden.
rock type: test.
major mineralogy: The specimen was acquired for joesmithite.

accompanying videos: Short videos featuring the mineral associations and optical properties of the joesmithite 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)
joesmithite
PPL: weak light-medium/medium yellow-brown pleochroism, high relief;
XP: up to 2nd order yellow δ;
with forsterite, calcite, and minor phlogopite, hematite and phosphatian hedyphane

 



left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-409
locality: The specimen is labeled “Blue Bell mine, Baker, California, USA”. However, apparently there may be more than one “Blue Bell mine” in the Baker area. The presumed locality for this sample is the “well-known for secondary Cu-Pb minerals” Blue Bell mine, ~14 km NW of the unincorporated community of Zzyzz (formerly Soda Springs) and ~12 km W of Baker.
rock type: test.
major mineralogy: The specimen was acquired for linarite and caledonite.

 



left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-410 (dealer sample number 7922)
locality: burned mine dump at Coal mine No. 45, Kopeysk, Chelyabinsk Oblast, Russia.
rock type: sanidinite-facies pyrometamorphic rock formed as a result of spontaneous coal fires.
major mineralogy: specimen acquired for “chlorohibschite” (alternatively known as “igumnovite”).

 



left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-411
locality: The sample is labeled with the general locality “Bellerberg, Eifel Volcanic Fields, Germany”, but is presumably more specifically from the Caspar quarry, the type locality for ferroindialite.
rock type: test.
major mineralogy: The specimen was acquired for ferroindialite.

 



left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-412
locality: Molinello Mine, Ne, Genoa, Liguria, Italy.
rock type: test.
major mineralogy: The specimen was acquired for marsturite.

accompanying videos: Short videos featuring the mineral associations and optical properties of the marsturite 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)
marsturite
PPL: patchy near colorless/pale orange/medium lemon-yellow pleochroism, high relief;
XP: up to 1st order orange-red δ;
with barite

 



left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-413 (dealer sample number 7539)
locality: Humpolec, Pelhřimov District, Vysočina Region, Czech Republic.
rock type: test.
major mineralogy: The specimen was acquired for malayaite.

 



left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-414
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).
major mineralogy: The specimen was specifically acquired for pabstite…

 



left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-415 (dealer sample number 8734)
locality: Itmurundy massif (Itmuryndy), Krasnyi Oktyabr’, Aktogay, Karaganda Region, Kazakhstan.
rock type: high pressure Na-metasomatite.
major mineralogy: specimen acquired for jadeite 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-416 (dealer sample number 8729)
locality: Sayano-Shushenskaya dam, Khakassia, Russia.
rock type: test.
major mineralogy: specimen acquired for jadeite.

 



left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-417
locality: Saidenbach reservoir, Forchheim, Pockau-Lengefeld, Erzgebirgskreis, Saxony, Germany.
rock type: test.
major mineralogy: The specimen was acquired for the rock type “saidenbachite”. Minerals present include quartz, K-feldspar, plagioclase, muscovite, biotite, pyrope, kyanite, and possibly coesite and diamond armored within the garnet and/or kyanite.

 



left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-418
locality: The sample is labeled with the general locality “Tanti, Córdoba Province, Argentina”, but presumably comes from the nearby Cerro Blanco pegmatite district. There are several pegmatite quarries in the area, and the only similar specimens pictured on mindat are reported specifically from the well-known El Criollo mine.
rock type: test.
major mineralogy: specimen acquired for phosphosiderite and jarosite.

 



left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-419 (dealer sample number 8834)
locality: from the type locality, Dannemora mine, Dannemora, Östhammar, Uppsala County, Sweden.
rock type: test.
major mineralogy: specimen acquired for clino-ferro-suenoite (formerly known as “dannemorite” or “manganogrunerite”).

accompanying videos: Short videos featuring the mineral associations and optical properties of the cummingtonite 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)
cummingtonite
PPL: very weak near colorless/very pale tan pleochroism, moderate-high relief;
XP: up to 1st order purple δ;
with opaques pyrrhotite and magnetite

 



left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-420
Cerchiara Mine, Borghetto Vara, Vara Valley, La Spezia Province, Liguria, Italy.
rock type: test.
major mineralogy: specimen acquired for aluminosugilite.

 



left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-421 (dealer sample number 6630)
locality: Titovskoe B deposit, Tas-Khayakhtakh Range, Polar Yakutia, Sakha, Russia.
rock type: test.
major mineralogy: specimen acquired for fluoborite.

 



left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-422
locality: The specimen is labeled Alta Peak, Clear Creek Canyon, San Benito Co., CA, USA. There are several small Cr deposits in the area, and the specific locality is not identified.
rock type: test.
major mineralogy: specimen acquired for uvarovite, clinochlore, and possibly ferchromide.

 



left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-423
locality: The original label lists “Amboahangy, Fort Dauphin, Madagascar”, which is not entirely geographically consistent. Further research supports that the sample is from a new discovery (November 2021) reportedly in the vicinity of Amboahangy, Amboasary Sud, Anosy, Madagascar. However, the exact locality is unclear, and one German dealer with extensive in-country experience with minerals from Madagascar, Jentsch Mineralien, alternatively lists either Amboahangy and Ampiha as localities for the roughly two dozen specimens offered for sale in February 2023 (although it’s not entirely clear that these names are geographically consistent either); note however that my specimen was purchased from a different dealer. For reference, the well-known Vohibola phlogopite deposit, the closest already-known locality for serendibite, is approximately 65 km S of the Amboahangy townsite. However, there appear to be numerous high-grade phlogopite-diopside occurrences widespread in the greater region, some with sapphirine, grandidierite and/or osumilite, that potentially could also host serendibite. In time as more material is brought to market, it’s possible a more precise locality will be discerned, and this locality entry will be updated as necessary.
rock type: test.
major mineralogy: specimen acquired for serendibite, quartz and phlogopite.

 



left image: plane-polarized light (E-W); right image: under crossed polarizers; use slider in center to view more of either image

sample: FKM-424
locality: Voronkafotra, Betroka, Anosy, Madagascar.
rock type: “sakenite”.
major mineralogy: specimen acquired for sapphirine and diopside.

accompanying videos: Short videos featuring the mineral associations and optical properties of the sapphirine 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)
sapphirine
PPL: near colorless/pale blue pleochroism, high relief;
XP: up to 1st order straw yellow δ, with anomalous blue overtones, especially in near optic axis sections;
with partially altered (pinitized) cordierite

 



upper left image: plane-polarized light (E-W); upper right image: under crossed polarizers; use slider in center to view more of either image

supplementary image: plane-polarized light (N-S)

 
sample: FKM-425
locality: Mirošov, Žďár nad Sázavou District, Vysočina Region, Czech Republic.
rock type: test.
major mineralogy: Specimen acquired for lucchesiite. Back-scattered electron (BSE) imaging indicates the tourmaline appears to be primarily one dominant composition, with additional small patches of lower z material. The main composition is barely ACa > ANa, but is sufficient to classify as a calcic tourmaline. FeT ≈ 2.3 apfu, but if Fe3+/∑Fe and ZMg are both unconstrained, multiple potential species assignments are possible across the ~0.16 to ~0.59 permissible range of Fe3+/∑Fe possible for this composition; fortunately compositional, structural and Mössbauer data reported by Bosi et al. (2017) offer these constraints. Mössbauer data from this study, and additional corroborating data reported from an earlier study, suggest Fe3+/∑Fe ≈ 0.50 ± 0.05. This value, coupled with a reported ZMg ≈ 0.5 to 0.6 apfu, derive a normalized formula consistent with lucchesiite (if one assumes less ZMg, then with greater resulting YMg, the composition normalizes to magnesio-lucchesiite instead). This example shows the necessity of knowing both Fe valence and atom site distributions to correctly assign the appropriate name; however, this also demonstrates the peril when one doesn’t have access to these more specialized techniques. This issue is further exemplified with respect to the minor lighter z composition regions in the tourmaline. ANa is notably greater than ACa, and so this composition is a sodic species. Permissible Fe3+/∑Fe for this composition can range from 0.062 to 0.630. Fe3+/∑Fe values from 0.062 to ~0.15 yield normalized formulas of magnesian schorl; Fe3+/∑Fe values from ~0.15 to ~0.34 yield normalized formulas of Fe-bearing dravite (depending in part on the actual [not the calculated] Mg distribution between the Y and Z sites). Beyond values of Fe3+/∑Fe greater than ~0.34, WO calculates to greater than 0.50 apfu, yielding various formulas (as an additional function of Mg site distribution) of “oxy”-type tourmalines that are not easily reconcilable with recognized “oxy” end-members; this is also the case if ones uses the “dominant composition” Fe3+/∑Fe best-estimate of 0.5. So instead for simplicity in this case, the minimum permissible Fe3+/∑Fe value of 0.062 is used here, yielding an unambiguous although not necessarily true-to-sample Mg-bearing schorl.

accompanying videos: Short videos featuring the mineral associations and optical properties of the varying compositions of the lucchesiite and plagioclase (“andesine”) 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)
lucchesiite
PPL: medium brown/opaque black pleochroism, moderate-high to high relief;
XP: up to 1st order yellow δ, but largely masked by body color of mineral;
with quartz, microcline/orthoclase, plagioclase, apatite, diopside and titanite
presumably U(-), but the appropriate orientation is too dark to obtain a figure (O = essentially opaque)
“andesine” (plagioclase)
PPL: colorless, low relief;
XP: up to 1st order white δ;
with quartz, microcline/orthoclase, minor apatite and “myrmekite” (intergrowth with quartz)

 



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