Smithsonite replacing Dolomite

specimen number:
9862003

location:
Rush, Marion Co., Arkansas, USA

description:
Rhombohedral crystals of what were once dolomite to 1.5 cm in size across the top of matrix and in the process of being replaced by crystallized smithsonite. In good condition. Classic material for this mining district.

The Rush mining district, located along the Buffalo National River in Marion County, Arkansas, has a rich history of zinc extraction that peaked during the late 19th and early 20th centuries, particularly around World War I. Geologically, the district is hosted within flat-lying Paleozoic limestones and dolomites, where carbonate replacement and hydrothermal groundwaters deposited significant zinc and lead ores. Mineralogically, the area is world-famous for its exceptional smithsonite specimens, including unique pseudomorphs where smithsonite replaced earlier rhombohedral dolomite crystals, creating hollow or coated crystal casts that display remarkable colors and crystal habits.

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