14 September 2013

Copper ring in datolite

Datolite is a calcium boron hydroxide nesosilicate, CaBSiO4(OH)... It is common in the copper deposits of the Lake Superior region of Michigan. It occurs as a secondary mineral in mafic igneous rocks often filling vesicles along with zeolites in basalt. Unlike most localities throughout the world, the occurrence of datolite in the Lake Superior region is usually fine grained in texture and possesses colored banding. Much of the coloration is due to the inclusion of copper or associated minerals in progressive stages of hydrothermal precipitation.
This specimen comes from the Tamarack Mineral Company in Calumet, Michigan, on the Keweenaw Peninsula where I went on an interesting rockhounding field trip several years


  1. I hadn't realized that you were a rockhound. I thought you just found these photos of pretty stones online and shared them with us.

    Do you have an extensive collection of minerals? Have you studied geology? When we lived in Colorado we used to drive up into the mountains nearly every weekend during the summer and I always wished that we knew more about geology and/or that we could take a geologist along with us to tell us what we were looking at...

    1. My rockhounding goes back decades; used to enjoy it when I was in Kentucky and in Texas, but I'm totally an amateur. I have a small collection of asbestiform minerals, but all of the mineral/crystal photos I've posted in the blog have been from sources found on the web.


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