WGNHS
Wisconsin Geological and Natural History Survey

Pyrope

Orange-red pyrope fragment in kimberlite matrix. Pyrope grain is about 4 mm across. Lake Ellen diatreme, near Crystal Falls, Iron County, Michigan. (Photo by W. Cordua.)

Formula: Mg3Al2(SiO4)3 Isometric

Description:

Pyrope is a magnesium-rich member of the garnet group found in rocks such as lamproites, anorthosite, serpentinite and their metamorphosed equivalents. It may survive weathering as a heavy detrital mineral. The chromium-rich member is considered an indicator mineral for diamond deposits.

KENOSHA COUNTY: Chrome pyrope occurs as in a subsurface, diamond-bearing lamprophyre diatreme, discovered within the outskirts of Kenosha (Carlson and Adams, 1997).