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Kernite
Chemical Formula	Na2B4O6(OH)2·3(H2O)
Species	Borates
Crystal System	Monoclinic
Mohs Scale	2
Specific Gravity	1.9-1.92
Color	Colorless, white
Streak	white
Luster	Vitreous
Refractive Index	n = 1.454 n = 1.472 n = 1.488
Diaphaneity	Transparent
Cleavage	PerfectOn perfect; less perfect; on fair. NOTE: The cleavable masses exhibit a simulated fibrous structure due to development of excellent cleavages. Cleavage fragments usually bent or warped around .
Fracture	Splintery
Crystal Habit：Crystalline - occurs as well-formed coarse sized crystals
Geological Setting：Sedimentary borate deposits.

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.

Kernite is soluble in cold water and alters to tincalconite when it dehydrates. It undergoes a non-reversible alteration to metakernite (Na₂B₄O₇·5(H₂O)) when heated to above 100° C.

Occurrence and history

The mineral occurs in sedimentary evaporite deposits in arid regions.

Kernite was discovered in 1926 in western 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 Kern County mine was the only known source of the mineral for many years. More recently, kernite was also discovered at and is now mined in Argentina and Turkey.

The largest documented single crystal of kernite measured 2.44x0.9x0.9 m³ and weighed ~3.8 tons.

Uses

Kernite is used to produce borax which can be used in a variety of soaps.