Kernite, also known as rasorite and hydrated sodium borate hydroxide (Na2B4O7·4H2O), is a colorless to white crystalline mineral that was formerly the chief source of borax. It is also the source of various boron compounds.
The mineral was discovered in 1926 in Kern County, California and later named for the county. Kern County was the only known source of kernite for many years but is now mined in Chile, Spain, and Turkey. More deposits are likely yet to be discovered, since this mineral is only found at great depths.
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