Browse Items (1651 total)

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This specimen is typical of the metaigneous charnockitic rocks associated with the massif anorthosites in the Adirondacks. With variation in the quantity of modal quartz, the rock qualifies as either a charnockite or a mangerite. Quartz content is…

This calcite marble is typical of most Adirondack metacarbonates. In the majority of instances, original dolomite has reacted to yield calcsilicates. Also present in these specimens are small, serpentinized droplets which may originally have been…

Metamorphised Briarcliff dolostone.

The thin section shows well-twinned dolomite grains with diopside at the bottom.

Metamorphised Briarcliff dolostone with visible micas. Contains diopside, tremollite, and phlogopite. At the metamorphic grade of the first sillimanite isograd.

Thin section shows irregular dolomite grains in the center, with pleochroic…

Metamorphised Balmville limestone with visible phlogopite crystals. Also contains actinolite.

Thin section shows calcite with interspersed pleochroic phlogopite.

Metamorphised Balmville limestone with visible phlogopite crystals. Also contains tremolite visible at the outcrop level. Within nose of anticline of Walloomsac schist.

The PPL thin section shows a large irregular calcite grain with tremolite at…

Hand Sample: Phaneritic rhyolite. 10% fine-grained phenocrysts of sanidine and quartz and 90% dark-brownish-red groundmass. Weathers to brown-orange.

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Hand Sample: Holocrystalline, phaneritic, fine-to-medium-grained quartz monzonite. Mineralogy includes large plagioclase laths up to 8mm in length, quartz, alkali feldspar, biotite. Very large crystals of a dark material up to 3cm in length.…

This lithology is characterized by 1-4 inch long megacrysts of microperthite in a groundmass of quartz, oligoclase, hornblende, orthopyroxene, garnet, and oxide. Although the contacts of this unit are everywhere conformable, the rock is believed to…

Hand Sample: Aphanitic light gray nephelinite containing some melilite. Melilite is the white minerals that range in size from 0.1 to 0.5cm. Sample contains numerous small sized (less than 0.05cm) vesicles that are evident on the cut face.