Browse Items (1651 total)

contact with wall rock is sharp and with very thin, chilled margin

This specimen displays an unusual and distinctive lithology that occurs primarily in lower, marble-rich units (for example, the Cedar River Formation).
Thin section shows quartz, K-feldspar and clinopyroxene.

orthoclase is concentrated in watery clear megacrysts with crushed borders

high-grade metamorphism

Image is of the North Side of the Tanzawa Mountains (Wikipedia)

This specimen is typical of the 5-10 foot thick coarse grained layers of glassy quartzites that comprise this formation. In most instances the quartzites are about 90% quartz. Feldspar and garnet are encountered locally. This is presumed to be the…

Metamorphised sandstone with a gray, glassy appearance. From the Paughquag quartzite, a late Cambrian formation. The basal Cambrian quartzite rests on pre-Cambrian gneisses.

The thin section shows quartz and plag with some biotite and grain…

This foliated sample is dominated by micas and quartz. It is a sample from the Hubbard Hill member.

Mica-based schist containing significant quartz

More orange in color that FR-3 (Red Chert). Radiolaria fossils are visible in thin section amongst red-orange martix.

(Thin Section FOV: 1.28)

Kingdom: Animalia Phylum: Chordata Class: Actinopterygii Order: Family: Genus: Species:

Red jasper matrix with interescting veins of while quartz. Prominent physcial weathering, brittle areas fall apart to the touch. Several prominent fractures run through the rock, contributing to the weakened structure. Most fresh surfaces are reddish…

Hand Sample: Holocrystalline, coarse-grained, phaneritic granite with dominant alkali feldspar crystals, as well as quartz and plagioclase feldspar. Veins or pockets of dark brown-black material dispersed intermittently.

Hand Sample: Holocrystalline phaneritic, porphyritic and granophyrite rich in alkali feldspar. Larger crystals or pockets of biotite and quartz also present. Rock is weathered to orange brown. Contact on one side with dark black-brown quartz-rich…

Red shale from the Indian River member of the Normanskill formation. This rock contains hematite, chlorite, muscovite, plagioclase, and quartz.

The thin section shows muscovite and biotite with some larger quartz grains visible and minor hematite…

Reddish chert and shale

Though listed as a limestone, this sample is best described as a conglomerate with calcite present in the matrix. This sample was collected from a bed of conglomerate lithology just below contact with Supai formation.

Both thin section images…

Fine-grained limestone with occasional fossil remains.

Both thin section images were taken at a 400x magnification.

Oblitic and Crinoidal Lithology.

Both thin section images were taken at a 400x magnification.

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