For what it's worth, the USGS does not specifically list any diatomite formation in Shasta County.
I cannot help but wonder if the DE was misidentified and instead was a volcanic material.
----- Original Message -----From: Lin KernsTo: Geology2Sent: Wednesday, January 30, 2013 2:08 PMSubject: Re: [Geology2] Diatomaceous Earth In That Volcanic Province?
LinOkay, Kimmer.. got it. Wherever these folks are digging must have been an ancient body of water. Volcanoes produce ash which is high in silicates. The ash falls into the water and the phytoplankton eat it, which produces those hard shells. The creatures die off after the food source is depleted, fall to the bottom. The cycle is repeated on a bell curve for population growth with each successive eruption. When the volcanoe goes dormant or becomes extinct, the diatoms die off, the water recedes and then you get a sedimentary bed of diatoms.Think that's what you are asking.