Browse Items (1651 total)

with sillimanite retrograde, bedding has been destroyed and turned into "soup"

Granite from the Spaulding Quartz Diorite. Thin section contains plagioclase, biotite, quartz, alkali feldspar, some garnet, and sillimanite. Hand sample shows quartz, feldspars, sillimanite, and mica.

Muscovite-biotite schist containing large sillimanite crystals-mostly retrograded to muscovite

Coarse

higher metamorphic grade than specimen one, lower than speciment 3

Muscovite-sillimanite schist where much of the sillimanite has been somewhat altered to muscovite. This sample may also contain muscovite pseudomorphs after staurolite.

The predominant lithology of the Peck Lake Formation is a sillimanite-garnet-biotite-quartz-oligoclase gneiss with pods and lenses consisting of two feldspars and quartz (anatectic?). The lithology is widespread throughout the Adirondacks and may…

This specimen is extremely rich in sillimanite. European geologists refer to such lithologies as "khondolites." This locality is very near some of the old graphite production sites west of Hague.
Thin section shows sillimanite, garnet, k-feldspar.

sillimanite-rich

Macroscopic: Low-grade metamorphic (zeolite facies) black siltstone with idiomorphic pyrite porphyroblasts. Microscopic: Very fine grained quartz and muscovite with large pyrite phenocrysts. Thin section picture in XPL unless noted in the picture…

Hand Sample: Holocrystalline, fine-to-medium-grained granite. Mineralogy includes potassium feldspar and quartz. One corner of rock has a mass of dark grey-brown groundmass with inclusions of plagioclase laths and anhedral grey-green crystals.…

Hand Sample: Porphyritic diabase with light crystals in a dark-grey-to-black groundmass. Plagioclase 45%, Pyroxene 45%, Hornblende 5%, Olivine and Biotite 5%

Macroscopic: Slate (low grade shale metamorphism) samples with visible thin black beds. Samples were found interbedded with siltstones represented by sample NS-1. High angle between bedding and cleavage. Microscopic: Very fine grained quartz,…

Kink fold in a slate from the Mt. Merino Member.

This rock is from the chlorite zone of the Barrovian metamorphic sequence (low metamorphism).

Black slate