Saturday, January 11, 2014

Guest article: Michigan Tech alumni discover new variety of Greenstone in the Keweenaw

By Shawn M. Carlson

While mineral exploration companies pore over maps and drill core data in the hopes of developing new mines in Michigan, others take a more academic approach and seek out new types of minerals, rare species not previously known to occur in our state -- like the recent discovery made by two Michigan Tech alumni, Shawn M. Carlson and Travis A. Olds.

This past summer Carlson, an industry mineralogist from Crystal Falls, Mich., and Olds, a Ph.D. candidate in environmental actinide chemistry at the University of Notre Dame, were prospecting around a long-abandoned mine near Copper Harbor and encountered something unusual.

"The discovery is a variety of pumpellyite -- the scientific name for Michigan’s state gemstone -- but this one has a lot of manganese in it, enough to transform its color from the traditional green into various shades of pink, tan, and brown," said Olds.

Thin transparent slice of Michigan greenstone (state gem) with watermelon-like, yellowish-green rim surrounding a pinkish-red, manganese-rich core. (Photo © and courtesy Shawn M. Carlson)

Manganese-rich "greenstones" are known from a few other worldwide localities, but this is the very first report of the material in Michigan and probably the first report in all of North America. Though of little interest to major mining firms, new mineral finds in the Keweenaw are uncommon and tend to generate a lot of discussion amongst lapidaries, rockhounds, and mineral artists.

"Discovering a mineral new to the state of Michigan is rare enough as it is, but to have that mineral be a new variety of our state’s official gemstone -- it’s pretty exciting," said Olds.

The discovery is part of an ongoing effort to advance our understanding of Michigan’s economic, environmental, and collectible mineralogy by documenting every type of mineral known to occur here, no matter how rare or common, large or small.*

*Author's Note: For details about this "Mineralogy of Michigan" project please see http://keweenawnow.blogspot.com/2013/05/guest-article-announcing-mineralogy-of.html.

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