metamorphic
Manhattan Schist
Manhattan Schist (Aluminous Metasedimentary Rock)
Mohs hardness of 6-7, typically grey to black with a silvery sheen due to mica flakes. Luster is pearly to sub-metallic. Exhibits prominent foliation and can contain porphyroblasts of garnet.
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Physical properties
Mohs hardness of 6-7, typically grey to black with a silvery sheen due to mica flakes. Luster is pearly to sub-metallic. Exhibits prominent foliation and can contain porphyroblasts of garnet.
Formation & geological history
Formed during the Taconic and Acadian orogenies (approx. 450-350 million years ago) through the metamorphosis of sedimentary shale and mudstone under intense heat and pressure.
Uses & applications
Primarily used as foundation support for New York City skyscrapers due to its extreme durability. Historically used as building stone for local walls and structures.
Geological facts
This rock is the bedrock of Manhattan. The depth of this schist influenced the New York skyline, as skyscrapers were built where the rock was closest to the surface. Features visible glacial striations from the last Ice Age.
Field identification & locations
Identify by its distinct glittery/silvery foliation planes (schistosity). Commonly found as outcroppings in Central Park, New York. Best identified by visible mica grains and resistance to weathering.
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