December 04, 2004

Epidote copy

Provided by: Heather Renyck, Milford High School, NH
Summary authors & editors: Heather Renyck; Jim Foster

The photo above showing epidote crystals in the Nahant Sill was taken in early October near Nahant, Massachusetts. This sill is believed to have cut through Avalonian rocks during the Ordovician Period (490 to 440 million years ago). Epidote crystals typically occur in high-pressure, low-temperature metamorphic rocks, especially those bearing calcium, and they may also occur as precipitates from magma in igneous formations. Epidote crystals are usually not exceptional in size or clarity, though some specimens produce outstanding gemstones. Coloring ranges from light green to dark green -- some are even dark brown or black, as illustrated above. The strap/ring is shown for scale.

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