|Crystal symmetry||Monoclinic prismatic
H-M symbol: (2/m)
Space group: P 21/c
|Unit cell||a = 7.0172(2) Å, b = 9.1582(2) Å, c = 15.6774(5) Å, β = 108.861(2)°; Z=4|
|Crystal habit||Crystalline - occurs as well-formed coarse sized crystals|
|Cleavage||Perfect on  and , good on |
|Mohs scale hardness||2.5-3|
|Luster||Vitreous - pearly|
|Specific gravity||1.9 - 1.92|
|Optical properties||Biaxial (-)|
|Refractive index||nα=1.454, nβ=1.472, nγ=1.488|
|Other characteristics||non-radioactive, non-fluorescent, non-magnetic|
Kernite, also known as rasorite is a hydrated sodium borate hydroxide mineral with formula Na2B4O6(OH)2·3(H2O). It is a colorless to white mineral crystallizing in the monoclinic crystal system typically occurring as prismatic to acicular crystals or granular masses. It is relatively soft with Mohs hardness of 2.5 to 3 and light with a specific gravity of 1.91. It exhibits perfect cleavage and a brittle fracture.
Occurrence and history 
The mineral occurs in sedimentary evaporite deposits in arid regions.
Kernite was discovered in 1926 in eastern Kern County, in Southern California, and later named for the county. The occurrence locale was the US Borax Mine at Boron in the western Mojave Desert. The type material is stored at Harvard University, Cambridge, Massachusetts, and the National Museum of Natural History, Washington, D.C.
The largest documented single crystal of kernite measured 2.44x0.9x0.9 m3 and weighed ~3.8 tons.
Media related to Kernite at Wikimedia Commons
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