Browse Items (1651 total)

Slightly metamorphosed greywacke

This charnockite is similiar to most of the Adirondack charnockites that occur interlayered with other metastratified units. Like its analogues, the Canada Lake charnockite shows conformable realationships with enveloping units. Mineralogically,…

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…

Coarse-grained hornblendite (some specimens have a few garnets)

This coarse-grained specimen is typical of the massive, homogeneous anorthosite that occurs within the Marcy Massif and underlies the High Peaks region of the Adirondacks. The anorthosite from Route 3 is best represented by analyses 5-L and 8, Table…

This specimen is typical of the olivine metagabbros that occur throughout the Adirondacks. These rocks are of great petrologic interest for they contain classic examples of garnet coronas and spinel-clouded plagioclase. Note the preservation of…

Blueschist from an outcrop in a stream bed

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.

The Sacandaga Formation consists of a well layered series of dark granulites (AD-12) and leucogneisses (AD-13). Orthopyroxene is generally present in greater quantity than clinopyroxene. It is not known whether these rocks are metasedimentary or…

This specimen is similar to the famous garnet deposits at Barton Mines at Gore Mountain. The garnets at Gore Mountain can attain diameters of 3 feet. At the Speculator road cut, garnet of 8-10 inches in diameter have been found, but smaller examples…

Pods and lenses of green diopsidite commonly occur along with the marbles. They are often composed of over 90% diopside.
Thin section contains diopside.

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…

This specimen is typical of the saturated gabbros of the Adirondacks. The plagioclases are generally in the range of Anâ‚„â‚€ and the orthopyroxenes average close to En₆₀. Antiperthite is locally developed. Scattered grains of ilmenite and garnet…

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…

This specimen consists of 50-60% andesine, 20-30% quartz, and minor pyroxene and hornblende. Associated with this lithology are 2-6 inch layers of pyroxene-plagioclase granulite and amphibolite. It is believed that the Royal Mountain Member gneiss…

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…

Minerals found in the calcsilicate facies contain quartz, diopside, enstatitic pyroxene, tremolite, calcite, and phlogopite. However, only a few thin sections have been found to contain all phases. In some specimens, the pyroxene is close to 100%…

(exotic block)