nesosilicates 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)
phenakite (FKM-288):
phenakite in granite pegmatite-associated Be-F metasomatite, with beryl and biotite mica
willemite (FKM-48):
[Mn-Mg]-bearing willemite (0.15 Mn2+ apfu; 0.14 Mg apfu) in high-grade calcareous Zn-Mn-metasomatite, with gahnite and franklinite
forsterite (FKM-112):
forsterite (1.89 Mg apfu) olivine in high-grade metasomatized dolomitic marble, with calcite, clinohumite and spinel
forsterite (FKM-113):
forsterite olivine in nephelinite, with nepheline
forsterite (FKM-114):
zoned forsterite (1.34 to 1.62 Mg apfu) olivine in olivine melilitite, with melilite, diopside clinopyroxene and nepheline
forsterite (FKM-148):
zoned forsterite (1.79 Mg apfu core; 1.09 Mg apfu rim) olivine in nephelinite, with diopside clinopyroxene and zoned Ti-rich magnetite-chromite
forsterite (FKM-162):
forsterite (1.77 Mg apfu) olivine in basalt-hosted spinel peridotite xenolith, with enstatite orthopyroxene, Cr-bearing spinel and Cr-bearing diopside clinopyroxene
forsterite (FKM-356):
forsterite olivine in high grade magnesian marble, with calcite
liebenbergite-forsterite ss
(FKM-392): zoned Mg-rich liebenbergite to Ni-rich forsterite olivine in historic anthropogenic slag, with trevorite-dominant spinel (opaque)
tephroite (FKM-43):
tephroite (1.47 Mn2+ apfu) olivine in high-grade calcareous Mn metasomatite, with calcite
monticellite (FKM-10):
monticellite (0.90 Mg apfu) olivine in high-grade skarn, with calcite
monticellite (FKM-298):
monticellite in sövite carbonatite, with calcite, fluorapatite and diopside clinopyroxene
monticellite (FKM-404):
monticellite in sövite carbonatite, with calcite and apatite
pyrope (FKM-266):
pyrope (1.96 Mg apfu) garnet in hydrated garnet peridotite, with magnesio-hornblende and diopside
almandine (FKM-23):
almandine (1.51 Fe2+ apfu; near pyrope composition boundary) garnet in granulite facies metapelite, with biotite mica, rutile, quartz, sapphirine, and sillimanite
spessartine (FKM-94):
Fe-bearing spessartine (0.95 Fe2+ apfu) garnet in granulite facies metasomatized-Mn-Zn-Pb exhalite, with clino-ferro-suenoite (formerly “manganogrunerite”) amphibole and minor Fe-bearing pyroxmangite
grossular (FKM-1):
V-bearing (0.10 V apfu) grossular garnet (“tsavorite”) in high-grade calc-silicate, with zoisite, diopside clinopyroxene, titanite and calcite
andradite (FKM-271):
Ti-bearing (0.53 to 0.68 Ti apfu) orange andradite garnet (heavily included with flamite) in pyrometamorphic sanidinite facies phosphatic metacarbonate, with melilite, apatite and kalsilite (note: thin section is slightly thick)
andradite (FKM-303):
minor-element-enriched andradite garnet (0.59 Mn2+ apfu; 0.01 As5+ apfu; 0.01 Zn apfu) in high-grade Zn-Mn-metasomatite, with bustamite, hardystonite, diopside (“jeffersonite”) clinopyroxene and willemite
uvarovite (FKM-149):
anomalously B(-) sector-zoned uvarovite (~1.16 Cr apfu) garnet in altered chromatite, with calcite and magnesiochromite
goldmanite (FKM-92):
Cr-bearing goldmanite (1.49 V3+ apfu; 0.17 to 0.28 Cr3+ apfu; 0.03 Y apfu) garnet in calcareous meta-U-V-metasomatite, with quartz, calcite and minor tremolite amphibole (note: low relief half of sample is epoxy)
kerimasite (FKM-404):
kerimasite garnet (1.34 VIZr apfu; IVFe3+:IVAl apfu ratio ≈ 1.00:0.90) in sövite carbonatite, with perovskite, fluorapatite and calcite
zircon (FKM-35):
zircon in nepheline-sodalite syenite, with sodalite, alkali feldspar, and aegirine clinopyroxene
zircon (FKM-305):
zircon in alkali feldspar microsyenite, with ferro-fluoro-katophorite amphibole, chevkinite-(Ce), fluorcalciopyrochlore, and Na-sanidine (K-feldspar)
sillimanite (FKM-23):
sillimanite in granulite facies metapelite, with hypersthene orthopyroxene, sapphirine and cordierite
sillimanite (FKM-116):
sillimanite in granulite facies metapelite, with biotite mica, quartz and garnet
sillimanite (FKM-232):
coarse sillimanite in granulite facies high-alumina metapelite, with corundum, microcline feldspar, rutile, biotite mica and quartz
andalusite (FKM-91):
B(+) pleochroic green Mn-bearing (0.15 Mn3+ apfu) andalusite (“viridine”) in mica schist, with quartz and muscovite
andalusite (FKM-163):
andalusite in a meta-“advanced argillic” metasomatite, with kyanite, muscovite and quartz
andalusite (FKM-328):
B(+) pleochroic yellow-green [Mn+Fe]-bearing andalusite (“viridine”; 0.06 VIMn3+ apfu & 0.05 VIFe3+ apfu) in Mn-rich metapelite, with quartz, plagioclase and mica
kanonaite/Mn-rich andalusite
(FKM-336): zoned kanonaite rims (0.73 VIMn3+ apfu) on Mn-rich andalusite cores (0.27 VIMn3+ apfu) in Mn-rich metapelite, with muscovite
kyanite (FKM-75):
kyanite in amphibolite facies meta-ferrolite, with quartz, Co-bearing staurolite and magnetite
kyanite (FKM-163):
kyanite in a meta-“advanced argillic” metasomatite, with andalusite, muscovite and quartz
kyanite (FKM-214):
kyanite in meta-advanced-argillite, with quartz
kyanite (FKM-273):
kyanite in a phosphate-rich meta-“advanced argillic” metasomatite
staurolite (FKM-32a):
Cr-bearing (0.14 Cr apfu) staurolite in amphibolite facies metapelite, with quartz and kyanite
staurolite (FKM-75):
anomalous blue Co-rich (0.38 Co apfu) staurolite (“lusakite”) in amphibolite facies meta-ferrolite, with quartz, kyanite and magnetite
yoderite (FKM-69b):
yoderite in eclogite facies whiteschist, with kyanite, quartz and talc
yoderite (FKM-307):
“green” yoderite in eclogite facies whiteschist, with anthophyllite amphibole, talc, hematite and rutile
yoderite (FKM-375):
yoderite in high grade whiteschist-associated amphibole schist, with amphibole, quartz and kyanite
“hydroxylhumite” (FKM-426):
“hydroxylhumite” (humite group) in high-grade metasomatic metacarbonate, with dolomite
chondrodite (FKM-36):
chondrodite (humite group) in high-grade metasomatic metacarbonate, with phlogopite mica and calcite
chondrodite (FKM-403):
norbergite (humite group) in magnesian marble, with norbergite and calcite
alleghanyite (FKM-243):
alleghanyite (humite group) in amphibolite facies calcareous meta-Mn-metasomatite, with kutnohorite, kellyite serpentine and galaxite spinel (note: thin section is cut somewhat thin)
clinohumite (FKM-112):
zoned clinohumite to hydroxylclinohumite (~8.55 Mg apfu; 1.18 to 0.62 F apfu; humite group) in high-grade metasomatized dolomitic marble, with calcite, forsterite olivine, spinel and phlogopite mica
clinohumite (FKM-184):
clinohumite (8.43 Mg apfu; 1.10 F apfu; humite group) in granulite facies B-bearing meta-carbonate, with calcite/dolomite (note: thin section is cut substantially thin)
clinohumite (FKM-364):
clinohumite in carbonatite-associated phlogopite metasomatite, with phlogopite
hydroxylclinohumite (FKM-356):
hydroxylclinohumite in high-grade magnesian marble, with spinel and calcite
chloritoid (FKM-142):
chloritoid in greenschist facies metapelite, with quartz and fine-grained phyllosilicates
titanite (FKM-2):
Sb-bearing (0.12 Sb apfu) titanite in meta-Mn-exhalite, with piemontite (epidote group) and quartz
titanite (FKM-165):
titanite in crustal “carbonatite”, with calcite, diopside clinopyroxene, apatite and phlogopite mica
ellenbergerite (FKM-258):
Zr-bearing ellenbergerite (Zr>Ti in weakly-colored areas; Ti>Zr in strongly-colored areas) in eclogite facies whiteschist, with pyrope garnet and talc
grandidierite (FKM-108):
grandidierite in high-grade B-bearing magnesian marble, with phlogopite mica
dumortierite (FKM-82):
dumortierite in peraluminous granite, with quartz and fibrous sillimanite
dumortierite (FKM-327):
dumortierite in B-bearing meta-advanced-argillic metasomatite, with quartz, muscovite and tourmaline
datolite (FKM-386):
datolite in B-bearing skarn, with Mn-rich ferrobustamite and hedenbergite pyroxene
gadolinite-(Ce) (FKM-370):
gadolinite-(Ce) in REE-metasomatite, with primarily “ferridiassakisite-(Ce)”-dollaseite-(Ce) ss
fluorbritholite-(Ce) (FKM-370):
fluorbritholite-(Ce) in REE-metasomatite, with “ferridiassakisite-(Ce)”-dollaseite-(Ce) ss, västmanlandite-(Ce) and gadolinite-(Ce)
no optic figure of useful quality was obtainable
spurrite (FKM-183):
spurrite in high-grade B-bearing meta-carbonate, with hillebrandite(?)
ternesite (FKM-435):
ternesite (polycrystalline pseudomorph after gypsum?) in pyrometamorphic sanidinite facies phosphatic metacarbonate, with primarily larnite, ye’elimite, spinel. Ancillary stage rotation PPL and XP videos at 500X

non-silicates 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