Dravite-Uvite

specimen number:
2062612

location:
Power's Farm, Pierrepont, St. Lawrence County, New York, USA

description:
Large lustrous sharply formed black crystals 7.0 cm in size on a crystallized quartz matrix. This is in terrific condition. Very fine large example from this classic locality. The specimen comes with a previous collection label from Ray DeMark.

Powers Farm in Pierrepont, St. Lawrence County, New York, is a world-renowned historical mineral locality recognized for over a century by collectors and geologists for producing exceptional tourmaline group specimens. Geologically situated within the Grenville Province of the Adirondack Mountains, the area features ancient metasedimentary rocks, such as marbles and calc-silicate gneisses, which underwent high-grade metamorphism and hydrothermal activity to form distinct crystal-bearing pockets containing quartz, tremolite, and members of the tourmaline supergroup. The tourmalines found at this classic site historically sparked scientific debate regarding their precise classification within the solid-solution series bridging dravite (the magnesium-rich, brown to black end-member) and uvite (the calcium- and magnesium-rich end-member), with modern analytical testing revealing that many crystals traditionally labeled as dravite actually fall into the uvite composition field due to high calcium concentrations.

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