Geologic units in Hamilton county, New York

Interlayered metasedimentary rock and granitic, charnockitic, mangeritic, or syenitic gneiss (Middle Proterozoic) at surface, covers 23 % of this area

Interlayered metasedimentary rock and granitic, charnockitic, mangeritic, or syenitic gneiss.

Charnockite, granitic and quartz syenite gneiss (Middle Proterozoic) at surface, covers 13 % of this area

Variably leucocratic, containing varying amounts of hornblende, pyroxenes, biotite; may contain interlayered amphibolite, metasedimentary gneiss, migmatite. Overprint signifies inequigranular texture or phacoidal structure.

Undivided metasedimentary rock and related migmatite (Middle Proterozoic) at surface, covers 10 % of this area

Undivided metasedimentary rock and related migmatite.

Biotite and/or hornblende granite gneiss (Middle Proterozoic) at surface, covers 9 % of this area

Locally pyroxenic; commonly with subordinate leucogranitic gneiss, biotite-quartz-plagioclase gneiss, other metasedimentary rocks, amphibolite, migmatite. Amphibolite with porphyroblasts of K-feldspar locally prominent in northwest Adirondacks. In northwest Adirondacks, grades into Yphg.

Biotite and/or hornblende granite gneiss (Middle Proterozoic) at surface, covers 8 % of this area

Locally pyroxenic; commonly with subordinate leucogranitic gneiss, biotite-quartz-plagioclase gneiss, other metasedimentary rocks, amphibolite, migmatite. Amphibolite with porphyroblasts of K-feldspar locally prominent in northwest Adirondacks. Overprint signifies inequigranular texture or phacoidal structure. In northwest Adirondacks, grades into Yphg.

Biotite-quartz-plagioclase gneiss (Middle Proterozoic) at surface, covers 4 % of this area

Commonly very low in biotite content, with interbedded feldspathic and biotitic quartzite and amphibolite; sillimanite and garnet common, graphite sporadic.

Biotite and/or hornblende granite gneiss (Middle Proterozoic) at surface, covers 4 % of this area

Locally pyroxenic; commonly with subordinate leucogranitic gneiss, biotite-quartz-plagioclase gneiss, other metasedimentary rocks, amphibolite, migmatite. Amphibolite with porphyroblasts of K-feldspar locally prominent in northwest Adirondacks. Overprint signifies inequigranular texture or phacoidal structure. In northwest Adirondacks, grades into Yphg.

Charnockite, mangerite, pyroxene-quartz syenite gneiss (Middle Proterozoic) at surface, covers 4 % of this area

Overprint signifies inequigranular texture.

Charnockite, mangerite, pyroxene-quartz syenite gneiss (Middle Proterozoic) at surface, covers 3 % of this area

Overprint signifies inequigranular texture.

Interlayered metasedimentary rock and granitic, charnockitic, mangeritic, or syenitic gneiss (Middle Proterozoic) at surface, covers 2 % of this area

Interlayered metasedimentary rock and granitic, charnockitic, mangeritic, or syenitic gneiss.

Quartz-feldspar gneiss (Middle Proterozoic) at surface, covers 2 % of this area

With variable amounts of garnet, sillimanite, biotite.

Charnockite, granitic and quartz syenite gneiss (Middle Proterozoic) at surface, covers 2 % of this area

Variably leucocratic, containing varying amounts of hornblende, pyroxenes, biotite; may contain interlayered amphibolite, metasedimentary gneiss, migmatite. Overprint signifies inequigranular texture or phacoidal structure.

Glacial and Alluvial Deposits (Quaternary) at surface, covers 2 % of this area

Underlying bedrock geology unknown.

Gabbroic or noritic metanorthosite (Middle Proterozoic) at surface, covers 2 % of this area

Dark mineral content in excess of 10 percent (part of unit Ya).

Undivided metasedimentary rock and related migmatite (Middle Proterozoic) at surface, covers 2 % of this area

Undivided metasedimentary rock and related migmatite.

Leucogranitic (alaskitic) gneiss (Middle Proterozoic) at surface, covers 1 % of this area

Sodic plagioclase ranges from generally subordinate to locally dominant; locally with biotite, hornblende, pyroxene, garnet, sillimanite, disseminated magnetite; commonly contains metasedimentary layers, amphibolite, migmatite; plagioclase-rich variety is host to magnetite ore bodies in eastern Adirondacks.

Quartz-feldspar gneiss (Middle Proterozoic) at surface, covers 1.0 % of this area

With variable amounts of garnet, sillimanite, biotite.

Hybrid rock: mangeritic to charnockitic gneiss (Middle Proterozoic) at surface, covers 1.0 % of this area

With xenocrysts of calcic andesine and, locally, xenoliths of anorthosite; with increasing percentage of anorthosite component, passes gradationally into anorthositic rocks.

Amphibolite (Middle Proterozoic) at surface, covers 0.9 % of this area

Commonly biotitic; garnetiferous, pyroxenic, in and adjacent to central massif of Adirondacks.

Calcitic and dolomitic marble (Middle Proterozoic) at surface, covers 0.9 % of this area

Predominantly; variably siliceous; in part with calcsilicate rock and amphibolite.

Metanorthosite and anorthositic gneiss (Middle Proterozoic) at surface, covers 0.8 % of this area

Mafic mineral percentage contoured in northwestern Marcy massif (St. Regis Quadrangle); contour value shown on high side of countoue line. See also Yach, Yack, Yamu.

Glacial and Alluvial Deposits (Quaternary) at surface, covers 0.7 % of this area

Underlying bedrock geology unknown.

Metanorthosite and anorthositic gneiss (Middle Proterozoic) at surface, covers 0.6 % of this area

Metanorthosite and anorthositic gneiss.

Metagabbro (Middle Proterozoic) at surface, covers 0.5 % of this area

Metagabbro, olivine metagabbro, derived amphibolite.

Amphibolite (Middle Proterozoic) at surface, covers 0.4 % of this area

Commonly biotitic; garnetiferous, pyroxenic, in and adjacent to Adirondack Highlands.

Interlayered gabbroic or noritic metanorthosite (Middle Proterozoic) at surface, covers 0.4 % of this area

Mangerite or charnockite, and the Yach lithology.

Quartzite, quartz-biotite schist and graphitic schist (Middle Proterozoic) at surface, covers 0.4 % of this area

In part feldspathic, micaceous, garnetiferous, sillimanitic.

Dolomitic and calcitic marbles interlayered with significant amounts of calcsilicate rock (Middle Proterozoic) at surface, covers 0.3 % of this area

Metasedimentary amphibolite, pyroxene granulite, and various gneisses; includes interlayered diopsidic and tremolitic marble and quartzite, and talc-tremolite rock (mined in Balmat-Edwards belt, northwest Adirondacks).

Leucogranitic gneiss (Middle Proterozoic) at surface, covers 0.2 % of this area

Sodic plagioclase ranges from generally subordinate to locally dominant; locally with biotite, hornblende, pyroxene, garnet, sillimanite, disseminated magnetite; commonly contains metasedimentary layers, amphibolite, migmatite; plagioclase-rich variety is host to magnetite ore bodies in eastern Adirondacks.

Beekmantown Group (Cambrian) at surface, covers 0.2 % of this area

Mohawk Valley: Little Falls Dolostone-chert; Hoyt Formation-limestone, dolostone, oolite. Washington county: Whitehall Formation-dolostone, limestone; Ticonderoga Dolostone-chert.

Mangerite, pyroxene-(hornblende) syenite gneiss (Middle Proterozoic) at surface, covers 0.1 % of this area

Mangerite, pyroxene syenite gneiss - pyroxene-(hornblende) syenitic gneiss; mesoperthite common. Overprint signifies inequigranular texture.

Interlayered amphibolite and granitic, charnockitic, mangeritic, or syenitic gneiss (Middle Proterozoic) at surface, covers 0.1 % of this area

Interlayered amphibolite and granitic, charnockitic, mangeritic, or syenitic gneiss.

Biotite-quartz-plagioclase gneiss, amphibolite, and related migmatite (Middle Proterozoic) at surface, covers < 0.1 % of this area

Locally sillimanitic; commonly garnetiferous in and adjacent to Adirondack Highlands.

Canajoharie Shale (Middle Ordovician) at surface, covers < 0.1 % of this area

Canajoharie Shale

Trenton and Black River Groups, undivided (Middle Ordovician) at surface, covers < 0.1 % of this area

Mohawk Valley: Dolgeville, Denley, Sugar River, Kings Falls, Glens Falls, Rockland, Amsterdam, and Lowville Limestones. Washington County: Glens Falls and Orwell Limestones.

Metagabbro (Middle Proterozoic) at surface, covers < 0.1 % of this area

Metagabbro, olivine metagabbro, derived amphibolite.

Potsdam Sandstone (Cambrian) at surface, covers < 0.1 % of this area

Potsdam Sandstone (Covey Hill in Quebec)