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Hunting Hill quarry (Rockville Crushed Stone Quarry; Travilah Quarry; Rockville Quarry; Bardon Stone Quarry; Aggregate Industries Quarry), Rockville, Montgomery Co., Maryland, USA

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Latitude & Longitude (WGS84): 39° 5' North , 77° 9' West
Latitude & Longitude (decimal): 39.0833333333, -77.15

A large active quarry (as of December, 2013) in the Ordovician-age Hunting Hill pluton. The pluton in the quarry is thought to be originally a dunite, now largely serpentinized. Gabbro dikes cutting the serpentinite have been converting via metasomatism to rodingite, a mixture of calcium-rich clinopyroxene (here a green chromium-rich diopside) and a pink to white grossular garnet. Shearing along the contacts between the more resistant rodingite and the weaker serpentinite as well as within the rodingite has provided space for veins and open-space fillings of a suite of bizarre often well-crystallized minerals. Over 60 minerals have been reported so far from the quarry, according to the excellent article by Parker (2005). Notable finds are red gemmy grossular crystals, coalingite masses, desautelsite, prehnite crystals, mcguinnessite and calcite crystals.

Mineral List

59 valid minerals.

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Griesbach, John (1956) Rockville Crushed Stone Quarry: Rocks and Minerals: 31: 351-353.

Bernstein, Lawrence (1980) Minerals of the Washington D. C. area: Maryland Geological Survey Educational Series 5, 148 p.

Parker, F. (2005), The Minerals of the Hunting Hill Quarry, Rockville, Maryland; Mineralogical Record 36 (5): 435-446.

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