Pyrite

specimen number:
2102369

location:
Rensselaer Quarry, Jasper Co., Indiana, USA

description:
Crystals of pyrite measuring to 2.5 cm in size across the front of a brecciated matrix. In good condition. Nice for this old locality.

The Rensselaer quarry, situated just east of the city of Rensselaer in Jasper County, Indiana, is a historically significant industrial aggregate operation known to regional mineral collectors as the Pleasant Ridge quarry. Geologically, the deposit consists of Paleozoic carbonate sedimentary sequences belonging to the Middle Devonian Muscatatuck Group, where thick beds of dolostone were subjected to late-stage structural fracturing and hydrothermal fluid circulation. This unique geochemical environment produced extensive open voids and mineralized crystal pockets heavily permeated by natural liquid bitumen, which frequently occurs as dark inclusions trapping fluid within highly lustrous calcite, dolomite, pyrite, sphalerite, and galena crystals. Historically, the site was opened as a commercial side-hill cut in the mid-twentieth century and was heavily worked by the Rensselaer Stone Company to produce crushed stone aggregate for regional highway construction. Active quarrying and milling operations continued for decades under federal oversight until the depletion of accessible commercial reserves and shifting local economics led to the permanent cessation of all aggregate extraction in the late twentieth century, after which the deep pit was allowed to naturally flood.

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