The 366 daily episodes in 2014 were chronological snapshots of earth history, beginning with the Precambrian in January and on to the Cenozoic in December. You can find them all in the index in the right sidebar. In 2015, the daily episodes for each month were assembled into monthly packages (link in index at right), and a few new episodes were posted from 2015-18. Beginning in May 2019, I'm adding short entries to the blog (not as podcast episodes, at least not for now, sorry!) mostly taken from the Facebook Page posts. Thanks for your interest!

Monday, May 13, 2019

Artinite and the Coast Ranges of California

The mineral is artinite, a magnesium carbonate that is an alteration product of high-magnesium serpentinites of the Diablo Range in central California. It’s from New Idria, a mercury (and other) mining district named for the historic Idria mercury mines now in Slovenia, which have been mined since 1490.

Tectonically, the New Idria area of California is in a fenster (German for window), a hole in a thrust sheet that is related to the collisions that produced the California Coast Ranges. Serpentine’s mechanical properties are such that it can flow – very slowly on human scales – and in places like Mt. Diablo and New Idria, it has risen buoyantly like a salt dome to breach the thrust sheet and bring the underlying serpentine to the surface.

The magnesium-rich serpentinite is part of the Coast Range Ophiolite – a word meaning “snake rock” for its often greenish color and scaly texture. Ophiolites are usually bits of oceanic crust that have been emplaced within or upon continental crust, and that’s what happened here. 

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