Category Inoborates Strunz classification 6.DB.05 Space group P21/c | Formula
(repeating unit) Na
2B
4O
6(OH)
2·3H
2O Crystal system Monoclinic | |
 | ||
Crystal class Prismatic (2/m)
(same H-M symbol) | ||
Kernite, also known as rasorite is a hydrated sodium borate hydroxide mineral with formula Na
2B
4O
6(OH)
2·3H
2O. 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.
Contents
Kernite is soluble in cold water and alters to tincalconite when it dehydrates. It undergoes a non-reversible alteration to metakernite (Na
2B
4O
7·5H
2O) 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 eastern Kern County, in Southern California, and later renamed after the county. The location was the US Borax Mine at Boron in the western Mojave Desert. This 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 a period of time. More recently, kernite is mined in Argentina and Turkey.
The largest documented, single crystal of kernite measured 2.44 x 0.9 x 0.9 m3 and weighed ~3.8 tons.
Uses
Kernite is used to produce borax which can be used in a variety of soaps.