Pyrite

specimen number:
2063728

location:
American Aggregates Corp. Quarry, Indianapolis, Marion Co., Indiana, USA

description:
A bright golden lustrous ball of crystallized pyrite with little attached matrix. In good condition all around. This is said to be replacing a brachiopod fossil. The specimen comes with a previous label from the collection of Ray DeMark. While this still appears very fresh and bright, and was collected in the 1990s, there is a bed of attached matrix that is starting to crumble to slightly.

The American Aggregates Corporation Quarry in Indianapolis, Marion County, Indiana, began operations over a century ago as a sand and gravel pit before transitioning into extensive crushed stone quarrying within the region's flat Paleozoic bedrock formations. Geologically, the site exposed sedimentary strata that yielded remarkable secondary mineralizations formed through localized reducing environments within the limestone and dolomite layers. The quarry achieved legendary status among Midwest mineral collectors specifically for its unique, highly sought-after crystallized pyrite. This pyrite typically occurs as distinct, freestanding spherical clusters, nodules, or modified octahedral and cubic crystal aggregates that formed without a point of attachment, sometimes replacing organic fossil material such as ancient bivalves. Because commercial quarrying operations eventually ceased and collecting access ended, these brilliant metallic brassy specimens remain cherished, highly prized classics of Indiana mineralogy.

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