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Glaucophane Glaucophane

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Glaucophane Glaucophane Amphibole Glaucophane UNC sample ? Rock type blueschist Locality unknown Note the purple to blue-gray pleochroism in the glaucophane in this slide. Glaucophane UNC sample ? Rock type blueschist Locality unknown Note the anomalous blue-gray interference colors in the glaucophane in this slide. Amphibole Hornblende UNC sample W-86 Rock type hornblende-cpx schist Locality unknown Note the characteristic ~120 degree cleavage angles in some sections and the brown to green. pleochroism. Hornblende UNC sample W-86 Rock type hornblende- cpx schist Locality unknown Note in some sections the ~120 degree cleavage angles which are diagnostic of amphiboles. Amphibole Tremolite UNC sample W-88 Rock type talc-tremolite schist Locality unknown Talc forms the fine-grained matrix between the prismatic crystals of tremolite in this rock. Note the ~120 degree cleavages in some of the tremolite sections. Andalusite UNC sample NM-1 Rock type andalusite-biotite schist Locality New Mexico This is an andalusite porphyroblast with poikiloblastic texture. Also note how the foliation (oriented roughly N-S in this view) is wrapped around the left and right corners of this grain, suggesting synkinematic growth of the andalusite porphyroblast. Mica Biotite UNC sample GSR X0720 Rock type garnet-mica schist Locality unknown Note the red-brown pleochroism and the characteristic black pleochroic haloes (caused by radiation damage). Biotite UNC sample GSR X0720 Rock type garnet-mica schist Locality unknown Note the anomalous red interference color. Mica Muscovite UNC sample GSR 1540 Rock type unknown Locality unknown Muscovite UNC sample GSR 1540 Rock type unknown Locality unknown This grain is shown at maximum birefringnence. Take a look at this grain at extinction to see muscovite's wonderful "bird's eye" mottling. Sericite (a fine-grained variety of muscovite) UNC sample BB-13 Rock type Alaskite Locality Montana The feldspars in this alaskite from the Boulder Batholith have been largely replaced by fine-grained muscovite (sericite). In this rock, sericite is a product of hydrothermal alteration. Calcite UNC sample GSR X5321 Rock type unknown Locality unknown Note the rhombohedral cleavage. Calcite UNC sample GSR X5321 Rock type unknown Locality unknown Note the rhombohedral cleavage and very high order interference colors. Chlorite UNC sample MIC-5c Rock type chlorite schist Locality Michigan Chlorite defines the foliation in this rock, which also shows some crenulation cleavage. Chloritoid UNC sample EU-310 Rock type chloritoid schist Locality ? This plane-light view highlights the sector zoning in these chloritoid porphyroblasts. Chloritoid UNC sample EU-310 Rock type chloritoid schist Locality ? These stubby crystals are chloritoid porphyroblasts. You can just barely see the anomalous green interference color at the edge of some of the grains. Despite the name, chloritoid really doesn't look anything like chlorite. Ellenbergerite UNC sample TS-40 (K. Stewart) Rock type qtz-ky-gt- musc schist Locality Dora Maira massif, Parigi, Italy The dark reddish-purple grain in the center of this photomicrograph is ellenbergerite, an extremely rare, high-pressure Mg-Al-Ti-silicate, which here forms an inclusion in nearly pure endmember pyrope garnet from the famous Dora Maira massif of Italy. Epidote UNC sample EU-81 Rock type Biotite granite gneiss Locality Moine, Scotland Note the fairly high relief of epidote, the highly fractured mineral in this photomicrograph. Epidote UNC sample EU-81 Rock type Biotite granite gneiss Locality Moine, Scotland Note the high-order interference colors of epidote. This slide is actually cut a little thin, and doesn't show the third-order colors that epidote may display in some sections. Microcline (K-feldspar) UNC sample GSR X1540 Rock type unknown Locality unknown Cross-hatched (or "tartan") twinning in microcline. Contrast this with polysynthetic twinning in plagioclase feldspar. Feldspar Plagioclase UNC sample WR-51 Rock type unknown Locality unknown This slide showcases one of plagioclase's very common features: its polysynthetic twinning. Contrast this with twinning in microcline (K- feldspar). Garnet UNC sample GSR X0720 Rock type garnet-mica schist Locality unknown Note the zonal distribution of quartz inclusions in this garnet porphyroblast. Garnet UNC sample GSR X0720 Rock type garnet-mica schist Locality unknown Note the zonal distribution of quartz inclusions in this garnet porphyroblast. Kyanite UNC sample NC-349 Rock type kyanite-garnet- mica schist Locality near Durham, NC Note the prismatic habit of kyanite. Kyanite UNC sample NC-349 Rock type kyanite-garnet- mica schist Locality near Durham, NC Note the first-order interference colors and prismatic habit of kyanite. Leucite UNC sample 1790 (card) Rock type leucite basalt Locality unknown Leucite UNC sample 1790 (card) Rock type leucite basalt Locality unknown Note the nearly isotropic nature of these leucite grains. Nepheline UNC sample H-99 Rock type nepheline basalt Locality unknown Many of the phenocrysts in this basalt are nepheline. Olivine UNC sample W-44 Rock type dunite Locality unknown Almost all of the grains in this rock are olivine. Note the high order interference colors and the minor secondary calcite. Augite (Clinopyroxene) UNC sample in "norite" card Rock type clinopyroxenite Locality West Point, GA Note the pigeonite twin lamellae in this grain. Pigeonite is a Ca-poor clinopyroxene. Augite (Clinopyroxene) UNC sample "norite" card Rock type clinopyroxenite Locality West Point, GA Note the pigeonite twin lamellae in this grain. Pigeonite is a Ca-poor clinopyroxene. Besides clinopyroxene's 2nd order colors, another way to distinguish clinopyroxene from orthopyroxene is by clinopyroxene's inclined extinction. Hypersthene (Orthopyroxene) UNC sample PP-12 Rock type bronzitite (orthopyroxenite) Locality Stillwater complex, MT Hypersthene can be identified from its characteristic rose-colored pleochroism which is exhibited by the grain in the center. Watch what happens to the color of this grain upon rotation of the stage. Hypersthene (Orthopyroxene) UNC sample PP-12 Rock type bronzitite (orthopyroxenite) Locality Stillwater complex, MT Orthopyroxenes are noted for having low, first-order interference colors. Also note the cleavages that intersect at about 90 degrees. Another identifying characteristic of orthopyroxene is its parallel extinction. Piemontite UNC sample ? Rock type unknown Locality unknown Piemontite has beautiful rose to yellow pleochroism. Piemontite UNC sample ? Rock type unknown Locality unknown Piemontite has beautiful, high-order interference colors. Quartz UNC sample GSR X1540 Rock type unknown Locality unknown Quartz UNC sample GSR X1540 Rock type unknown Locality unknown This slide shows quartz in a range of crystal orientations, all having low- first order interference colors. Coesite UNC sample TS-41 (K. Stewart) Rock type qtz-ky-gt-musc schist Locality Dora Maira massif, Parigi, Italy Coesite (center of inclusion) and recrystallized quartz (borders of inclusion) form a tiny inclusion in nearly pure endmember pyrope garnet from the famous Dora Maira massif of Italy. The presence of coesite (a high-pressure polymorph of quartz) indicates that this rock saw extremly high pressures during metamorphism (probably more than 28 kbar). Quartz after coesite UNC sample TS-42 (K. Stewart) Rock type qtz-ky-gt-musc schist Locality Dora Maira Massif, Parigi, Italy The region of coarser-grained quartz in the upper center portion of this photomicrograph was probably originally occopied by coesite, the high- pressure polymorph of quartz. Metamorphic rocks from the Dora Maira Massif show other evidence of being exhumed from EXTREMELY deep levels in thickened crust. Staurolite UNC sample EU-17 Rock type staurolite- kyanite - garnet-mica schist Locality ? The "swiss cheese" look (i.e., poikiloblastic texture) of these staurolite porphyroblasts is typical for this mineral. Also note the strong banana yellow pleochroism. Staurolite UNC sample EU-17 Rock type staurolite- kyanite - garnet-mica schist Locality ? The "swiss cheese" look (i.e., poikiloblastic texture) of these staurolite porphyroblasts is typical for this mineral. Stilpnomelane UNC sample L-11 Rock type garnet-stilp- muscovite schist Locality ? Stilpnomelane looks alot like biotite (same habit and color) but lacks the "bird's eye" extinction that biotite displays. Actually, the stilpnomelane in this slide has a more acicular habit than most biotite. Stilpnomelane UNC sample L-11 Rock type garnet-stilp- muscovite schist Locality ? Stilpnomelane looks alot like biotite (same habit and color) but lacks the "bird's eye" extinction that biotite displays. Actually, the stilpnomelane in this slide has a more acicular habit than most biotite. Talc UNC sample W-88 Rock type talc-tremolite schist Locality unknown Talc forms the fine-grained matrix between the prismatic crystals of tremolite in this rock. Note the fine-grain size and the extremely high interference colors of the talc. Titanite (Sphene) UNC sample EU-290 Rock type syenite Locality ? Titanite typically forms wedge-shaped crystals like this one. Also notice the extremely high relief. Titanite (Sphene) UNC sample EU-290 Rock type syenite Locality ? Titanite typically forms wedge-shaped crystals like this one. Also notice the extremely high interference colors. Tourmaline UNC sample ? Rock type unknown Locality unknown This slide shows zoned trigonal cross-sections and elongate sections. Note green to brown pleochroism. Tourmaline may also display bluish pleochroism. Tourmaline UNC sample ? Rock type unknown Locality unknown This slide shows extinct trigonal cross-sections and elongate sections displaying maximum birefringence. The matrix is quartz. Vesuvianite (Idocrase) UNC sample CA-75 Rock type ? Locality ? A fairly uninteresting photo here. Vesuvianite (Idocrase) UNC sample CA-75 Rock type ? Locality ? Vesuvianite displays the deepest indigo blue anomalous interference colors you've ever seen! .
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