Browse Items (1651 total)

Hand Sample: Hypocrystalline, porphyritic rhyolite. 20% subhedral to anhedral biotite, quartz, and microcline (sanidine) phenocrysts. 80% grey-brown groundmass. Massive.

Hand Sample: Holocrystalline, fine-grained phaneritic granite with crystals of potassium feldspar and smoky quartz. Weathers to orange-brown and light-gray.

1:24000

1:24000

Mostly quartz, oligoclase, and microcline

1:24000

1:24000

Hand Sample: Porphyritic rhyolite with medium-grained Potassium feldspar phenocrysts in a brown-red groundmass. Weathers to yellow-brown.

Macroscopic: Staurolite, garnet, biotite porphyroblastic, chlorite bearing, muscovite schist. Both garnets and staurolite are idiomorphic with the former highly poikiloblastic. The foliation in the schist bends around the porphyroblastic phases…

Sillimanite has been partly psuedomorphed

Moslty conglomerates, but partly staurolite rimmed with muscovite

Some remnants of andalusite

Staurolite rimmed with muscovite

Isoclinal folding and cross bedding, spelitic and sandy beds all present

includes some sillimanite and occurs in distinct bands

Mica-based schist with porphyroblasts of staurolite.

Schist with coarse staurolite grains. This outcropping is approximately on the strike of the chloritoid schists (sample 7). Also contains garnet, muscovite, feldspar, and quartz. Presumed to be from the Everett Schist.

The thin section shows…

Mineralogy: quartz, feldspar, biotite, staurolite. Foliated. Foliation caused by biotite, staurolite is porphyroblastic. Biotite-staurolite-schist. Staurolite Zone.

Schist bearing both staurolite and chloritoid. This marks the first appearance of staurolite in the metamorphic sequence. Also contains garnet, muscovite, chlorite, biotite, feldspar, and quartz. The assemblage in not in equilibrium.

The thin…