Forsterite

specimen number:
2062156

location:
Kimberlite 73, Hermansville, Menominee Co., Michigan, USA

description:
A plastic vial full of small grains of green translucent forsterite, the variety known as peridot. The size provided is the size of the vial. Unusual locality example for the species.

The Kimberlite 73 pipe, located near Hermansville in Menominee County, Michigan, is part of a cluster of ultrapotassic igneous bodies discovered in the northern Great Lakes region. Geologically, this site represents a volcanic pipe composed of kimberlite, which intruded through the Paleozoic sedimentary cover and into the Precambrian basement approximately 380 million years ago during the Devonian Period. The rock is characterized by a fragmented, brecciated texture containing macrocrysts of magnesium-rich ilmenite, pyrope garnet, and chrome diopside, which are classic indicator minerals for diamond-bearing potential. Historically, the pipe was identified in the early 1970s following regional geophysical surveys and heavy mineral sampling conducted by minerals exploration companies. While extensive core drilling and bulk sampling were performed to evaluate the diamond grade, the deposit was ultimately determined to be sub-economic for full-scale commercial mining. Today, the site remains an important locality for researchers studying the tectonic history and mantle composition beneath the Michigan Basin.

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