Kernite
Hydrated sodium borate mineral used to produce borax.
Kernite, also known as rasorite, is a hydrated sodium borate hydroxide mineral with formula Na2B4O6(OH)2·3H2O. 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 a Mohs hardness of 2.5 to 3 and light with a specific gravity of 1.91, exhibiting perfect cleavage and brittle fracture.
- field
- Mineralogy
- known_for
- Source of borax used in soaps
- hardness
- 2.5 to 3 (Mohs)
- specific_gravity
- 1.91
- crystal_system
- Monoclinic
Lore & Background
The location was the US Borax Mine at Boron in the western Mojave Desert. Type material is stored at Harvard University and the National Museum of Natural History. The Kern County mine was the only known source for a period of time; more recently, kernite is mined in Argentina and Turkey. The largest documented single crystal measured 2.44 x 0.9 x 0.9 m³ and weighed about 3.8 tons.
Reader's Guide
Kernite is significant as a mineral source of borax, which is used in a variety of soaps. The mineral occurs in sedimentary evaporite deposits in arid regions, and its largest known crystal weighed approximately 3.8 tons. While initially only found in Kern County, subsequent mining in Argentina and Turkey expanded its availability. The mineral's perfect cleavage and brittle fracture, along with its low hardness and specific gravity, define its physical characteristics. Its legacy lies in its role as a borax ore, supporting industrial applications, and its type specimens preserved in major museums.
Did You Know?
- Kernite is also known as rasorite.
- The largest documented single crystal of kernite weighed about 3.8 tons.
- Kernite alters to tincalconite when it dehydrates.
Frequently Asked Questions
What is Kernite?
Kernite, sometimes called rasorite, is a hydrated sodium borate hydroxide mineral with the chemical formula Na₂B₄O₆(OH)₂·3H₂O. It belongs to the mineralogy field and is best known as a borax-bearing species.
What does Kernite look like in hand specimens?
It typically presents as colorless to white prismatic or acicular crystals, though granular masses are also common. The mineral crystallizes in the monoclinic system, giving its crystals a distinctly angular, non-cubic appearance.
How hard and heavy is Kernite?
Kernite sits at a Mohs hardness of roughly 2.5 to 3, making it soft enough to scratch with a copper penny or a fingernail in some cases. Its specific gravity is only 1.91, so it feels notably light for a mineral, and it shows perfect cleavage with a brittle fracture.
Why is Kernite important to industry?
Its primary practical role is serving as a natural source of borax, which is then processed into products such as soaps and other household cleaning agents. Without borate minerals like Kernite, the borax supply chain would lack one of its key raw-material inputs.
How does Kernite differ from other borate minerals?
Kernite is distinguished by its specific hydrated sodium-borate hydroxide composition and its monoclinic prismatic habit, setting it apart from more common borates like ulexite or colemanite. Its relatively low hardness and light specific gravity also make it easier to identify in the field than harder borate species.
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