magnesite - teaching hand specimen of very light gray to white earthy magnesium carbonate from the Kramer Hills

Magnesite - MgCO₃

Magnesite, magnesium carbonate, can be earthy or crystalline. This earthy magnesite was formed through hydrothermal alteration of Miocene (?) lake beds, though it can also form in irregular veins and masses through the alteration of serpentine by water containing carbonic acid. 

A gold strike in February 1926  turned Kramer Hills into a boomtown - for about a year and a half. The initial strike petered out and later prospectors had no luck. But for a little over a year, the mining camp of Kramer Hills had a grocery store, bakery, hotel, pool hall, sign shop, radio shop, several cafes, two dance halls, a lighting plant for electricity, a telephone exchange, and a newspaper. The April 22, 1926 issue of The San Bernardino Sun reported that gold was being panned freely in many prospect holes, but summer heat and unproductive prospects put an end to most of the mining.

After the excitement subsided, the Kramer Hills magnesite deposit was explored in the 1930s by the Ball (Red Seal) Chemical Company. A number of prospects have been opened since then, but it appears that commercial production was small. Magnesite has a commercial application in the manufacture of brick and furnace linings and as a source of magnesium. This magnesite occurs in association with a tan chert that we often have in stock and occasionally has included flakes of biotite mica.

Historical photos of the Kramer Hills Mining Camp 1926 by Charles Puck, from the collection of The Huntingtion Library.

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