• Specimen Number

  18

• Description

  Cut and polished quarried slab of serpentenite with intergrowths and veins of other rock. As described elsewhere, serpentine is a hydrated magnesium silicate mineral with a greasy/waxy luster and a complex chemical formula. This rock was intensely fractured during at least four cross-cutting events visible in the stone. Identified by staff of the Maryland Survey who said such rock is found throughout the state.

• Classification

  Metamorphic.  Serpentinite.

• Location & Occurrence

  Found throughout the state.  Formed by obduction of the Baltimore Mafic Complex ca. 450 Ma from a reaction involving hot saline water and   mafic volcanic rocks.   Such situations are called ophilities, created by scraping off of the sea floor during subduction.

• Geological Age

  450 Ma.

• Geoheritage

  Serpentinite is named for its greenish color, as with many common snakes of vegetated areas.  Barrens produced by weathering chemistry. Most of the rock easily dissolves, leaving only thin,, easily eroded, barrens that are sparsely vegetated.  This rock was also mined for chromite.

• Links

  Link to State Geological Map from USGS.  Link to Maryland Geological Survey .

• Other

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