Tuesday, March 20, 2012

Visiting the California Blue mine

Recently, Alyssa visited the California Blue mine in San Bernardino County, California.  This is relatively new discovery of a pegmatite practically in our backyard!  Mine owner Dave and partners have been working the mine for a few years.  So far they have found some nice gemmy aquamarines, water clear topaz and nice smoky quartz specimens!

This is one of the nicer aquamarines to come out recently, photo courtesy of Jeff Scovil

Here are a couple pictures of the pegmatite, you can see a big aquamarine crystal in the feldspar matrix on the left.  I don't know what type of pegmatite this is, in addition to the minerals already mentioned, I saw phlogopite (mica) and one of the garnets, probably spessartine.  No tourmaline, not even schorl.

This is Dave, the mine owner, hard at work.  Trying to get a few more hours in before the rain hits!

In pegmatite you can find what are called "gem pockets"  These are cavities in the rock that fill with hot water (or water-rich fluid - not magma, not that hot)  As the fluid cools, minerals drop out of solution and begin to crystalize as solids.  Because there is free space the minerals can grow large without bumping in to other minerals that impede their growth.   Once the pockets cool,  the water drains away and then many years of groundwater percolation carry small sediment particles and the pockets fill with mud!  That's what they look for, the pockets can yield the most crystals and the nicest crystals.  This is mineral dealer Rick Kennedy, using his preferred tool (chopsticks) to dig through the pocket mud.  The following video shows how he does it:

Here's Rick again with a big interesting feldspar crystal, thanks Dave and Rick for the great tour, happy digging!

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