non-silicates in thin section


Check out the video atlas of minerals in thin section introduction page for some background on how these videos were prepared and processed, and for additional useful information on the included table content, the search tab, and other user-adjustable features. There is also an accompanying illustration to assist viewers with determining 2V° values from the BxA or optic axis figures in the “optic figures” videos.

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The Vimeo-hosted versions of these video are also search-engine discoverable, and can be found by searching for the term “thin section” coupled with the sample number (e.g. “thin section FKM-49”), with or without also including the accompanying mineral name. YouTube-hosted versions of these videos are no longer search-engine discoverable (in protest of YouTube polluting even short educational videos with non-optional ads… grrr!), but can still be found organized in playlists on my rockPTX YouTube channel.


mineral PPL (lower
polar rotation)
(stage rotation)
(stage rotation)
optic figure
(stage rotation)
zincite (FKM-20):
zincite in high grade calcareous Zn-Mn metasomatite, with calcite and franklinite
corundum (FKM-78):
corundum (slightly thick due to extreme hardness) in high grade low-silica feldspathic gneiss, with biotite, plagioclase and alkali feldspar
corundum (FKM-290):
Cr-bearing (0.01 Cr apfu) ruby variety of corundum (slightly thick due to extreme hardness) in high pressure meta-gabbroid, with epidote and zoisite (note: optic axis figure is far off-center due to lack of ideally-oriented crystals)
rutile (FKM-273):
coarse rutile in phosphate-rich meta-advanced-argillite, with burangaite and berlinite
baddeleyite (FKM-191):
baddeleyite in granulite facies high-alumina metasomatic “plagioclasite”, with anorthite feldspar and corundum
spinel (FKM-106):
Cr-bearing (0.77 Mg apfu; 0.24 Cr apfu) spinel in carbonatite-associated damtjernite dike, with calcite, serpentine, amphibole and phlogopite
spinel (FKM-162):
Cr-bearing (0.78 Mg apfu; 0.18 Cr apfu) spinel in basalt-hosted spinel peridotite xenolith, with forsterite olivine and Cr-bearing diopside clinopyroxene
spinel (FKM-191):
spinel in granulite facies aluminous calc-silicate, with anorthite
spinel (FKM-290):
Cr-bearing (0.51 Mg apfu; 0.17 Cr apfu) spinel in high pressure meta-gabbroid, with Cr-bearing pargasite amphibole, corundum, zoisite and aluminous vermiculite clay
hercynite (FKM-46):
hercynite (spinel group) in granulite facies B-bearing metapelite, with partially altered cordierite
hercynite (FKM-263):
hercynite (spinel group) in Al-rich “calc-skarnoid”, with vesuvianite and calcite
gahnite (FKM-12):
gahnite (spinel group) in high grade Zn-bearing meta-quartzite, with quartz
gahnite (FKM-48):
gahnite (spinel group) in high grade calcareous Zn-Mn metasomatite, with franklinite and tephroite
chrysoberyl (FKM-156):
chrysoberyl in greenschist facies meta-blackwall, with phlogopite and chlorite
srebrodolskite (FKM-383):
srebrodolskite (1.27 Fe3+ apfu) in sanidinite facies paralava, with gehlenite and larnite
grossite (FKM-202):
pleochroic V-bearing (0.01 V apfu) grossite in probable slag, with hibonite, intergrown K- & Na-dominant diaoyudaoite(?) and vanadium
hibonite (FKM-191):
hibonite in granulite facies aluminous calc-silicate, with spinel, anorthite plagioclase and corundum
presumably U(-)
but no optic figure available
hibonite (FKM-263):
hibonite in Al-rich “calc-skarnoid”, with vesuvianite and calcite
(FKM-75): pleochroic violet Co-dominant (0.88 Co apfu) högbomite (“cobaltohögbomite”) in amphibolite facies meta-ferrolite, with quartz and magnetite (100X)
presumably U(-)
but no optic figure available
diaoyudaoite(?) (FKM-202):
intergrown mixed K- and Na-dominant diaoyudaoite(?) in probable slag, with hibonite, grossite and vanadium
wodginite (FKM-217):
wodginite in granite pegmatite, with albite and Li-bearing mica
presumably biaxial
but no optic figure available
(FKM-41): zoned pyrochlore in sövite carbonatite, with apatite, diopside clinopyroxene and calcite
(FKM-104): fluorocalciomicrolite in Li-Ta-enriched granite pegmatite, with Li-muscovite mica and microcline K-feldspar
fluorite (FKM-146):
color-zoned fluorite in agpaitic nepheline syenite (“lakarpite”), with arfvedsonite amphibole, nepheline and rosenbuschite
fluorite (FKM-315):
color-zoned fluorite in metamorposed agpaitic syenite, with alkali feldspar (microcline host & coarse albite patches) and omphacite/aegirine-augite clinopyroxene
cryolite (FKM-208):
cryolite in F-rich segregation in granite, with quartz, siderite and Fe-oxyhydroxide
presumably B(+), but the birefringence was too low to obtain a useable figure
magnesite (FKM-210):
magnesite in Mg-metasomatite
calcite (FKM-298):
anomalously biaxial calcite in sövite carbonatite, with fluorapatite. The slight deviation from uniaxial optics is presumably due to crystal strain
rhodochrosite (FKM-190):
rhodochrosite in high grade meta-Mn-metasomatite, with proto-ferro-suenoite (formerly “proto-mangano-ferro-anthophyllite”) amphibole, quartz, spessartine garnet and pyroxmangite
siderite (FKM-208):
siderite in F-rich segregation in granite, with quartz, cryolite and Fe-oxyhydroxide (as an alteration of siderite)
dolomite (FKM-115):
Fe-bearing dolomite (0.09 Fe apfu in greenschist facies meta-altered-ultramafic, with clinochlore chlorite
ankerite (FKM-66):
zoned ankerite-dolomite in carbonatite, with sodalite
dawsonite (FKM-66):
dawsonite in carbonatite, with sodalite and zoned ankerite-dolomite
stichtite (FKM-197):
stichtite (perhaps admixed with optically-similar barbertonite) in Cr-bearing serpentinite, with serpentine
fredrikssonite (FKM-242):
fredrikssonite in high-grade Mn-metasomatite, with calcite/dolomite, adelite, and opaque jacobsite-Q (note: thin section is cut somewhat thin)
presumably B(+)
but crystals were too dark to obtain an optic figure
warwickite (FKM-184):
warwickite in granulite facies B-bearing meta-carbonate, with calcite/dolomite and clinohumite (note: thin section is cut substantially thin)
henmilite (FKM-377):
henmilite in sanidinite facies B-bearing meta-carbonate, with undifferentiated Ca borates
olshanskyite (FKM-284):
olshanskyite in borate skarn, with sakhaite and additional undifferentiated hydrous borates
sakhaite (FKM-284):
sakhaite in borate skarn, with coarse veinlet of olshanskyite and additional undifferentiated hydrous borates
manganberzeliite (FKM-228):
manganberzeliite in metasomatized meta-Mn-exhalite, with calcite and quartz
isotropic (some grains anomalously birefringent)
schäferite (FKM-392):
schäferite in historic anthropogenic slag, with plagioclase (to be confirmed)
isotropic (some areas anomalously birefringent)
berlinite (FKM-273):
berlinite (isostructural with quartz and optically similar, but with low negative relief) in phosphate-rich meta-advanced-argillite, with trolleite and kyanite that is rimmed by other Al-phosphates
adelite (FKM-242):
adelite in high-grade Mn-metasomatite, with dolomite, hydroxylclinohumite, and opaque jacobsite-Q (note: thin section is cut somewhat thin)
wagnerite (FKM-214):
wagnerite in phosphate-rich meta-advanced-argillite, with lazulite and quartz
fluorapatite (FKM-41):
apatite in sövite carbonatite, with diopside clinopyroxene and calcite (apparent weak “pleochroism” due to accidental stray polarization)
lazulite (FKM-163):
lazulite in a meta-“advanced argillic” metasomatite, with andalusite, kyanite, muscovite and quartz
lazulite (FKM-214):
lazulite in phosphate-rich meta-advanced-argillite, with wagnerite, kyanite and quartz
scorzalite (FKM-273):
atypical pleochroism scheme (and also anomalously low 2V°) low-Mg (0.02 to 0.07 Mg apfu) scorzalite in phosphate-rich meta-advanced-argillite, with kyanite and trolleite
trolleite (FKM-273):
trolleite in phosphate-rich meta-advanced-argillite
burangaite (FKM-273):
burangaite in phosphate-rich meta-advanced-argillite, with kyanite, trolleite, berlinite and additional Al-rich phosphates
vivianite (FKM-385):
vivianite in phosphate-rich granite, with additional Fe-phosphates, muscovite, quartz and zinconigerite-2N1S

nesosilicates in thin section

sorosilicates and cyclosilicates in thin section

single chain inosilicates in thin section

double chain and more complex inosilicates in thin section

phyllosilicates in thin section

tectosilicates and miscellaneous silicates in thin section