Calcite

specimen number:
2013523

location:
Cavestone Quarry, Norristown, Indiana, USA

description:
An outstanding example for this Indiana locality. Large orange semi lustrous slightly translucent crystals of calcite set nicely up on matrix. In great condition. Really nice color on this one. This exhibits a large basal pinacoid termination.

The Cavestone Quarry is located near Norristown in Shelby County, Indiana, and serves as an important industrial site for the extraction of carbonate rock within the Illinois Basin. Geologically, the quarry primarily exposes the Middle Silurian-aged Louisville Limestone and the overlying Mississinewa Shale member of the Wabash Formation. These rock units were deposited approximately 420 to 430 million years ago in a shallow, marine shelf environment characterized by reef-building activity and carbonate mud accumulation. The mineralization at this site occurred as hydrothermal fluids migrated through regional joint sets and fossiliferous horizons, depositing minerals in open vugs and along bedding planes. Historically, the quarry has been a long-term provider of crushed stone for construction, road aggregate, and agricultural applications in central Indiana. For mineral collectors, the site is recognized for producing aesthetic specimens of lustrous calcite, often found in association with brassy pyrite and occasional dolomite crystals within the vuggy limestone matrix.

For mineral collectors, the Cavestone Quarry typically produces sharp, colorless to white calcite crystals that exhibit a clean, vitreous luster. These standard specimens are frequently found as rhombohedral or scalenohedral forms, often occurring in dense clusters within the limestone vugs. However, a very specific and unusual find at this locality consists of calcite crystals with a distinct, rich orange coloration. This orange hue is not the common appearance for Norristown material, making such specimens a notable departure from the typical colorless variety. The orange crystals tend to be translucent rather than transparent, possessing a saturated tone that provides a bold contrast against the grey host rock. Whether in the common colorless form or the rare orange variation, these calcites represent the specific geochemical conditions present during the post-depositional history of the Shelby County strata.

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