Kernite is a rare sodium borate mineral typically found as large, colorless to white prismatic crystals in evaporite deposits. It is known to dehydrate upon exposure to air, often altering into a white powder of tincalconite, so specimens should be kept in sealed containers. It is most famous for its occurrences in the Kramer borate deposit in California.

Hardness

2.5

Mohs

Luster

Vitreous, satiny on fibrous cleavages

Streak

White

Transparency

Transparent

mineraluncommon

Kernite

Also: rasorite

Hardness: 2.5
Luster: Vitreous, satiny on fibrous cleavages
Streak: White
Transparency: Transparent

Is this kernite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch kernite with a known reference. Kernite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous, satiny on fibrous cleavages.
4
Match the color range
Compare against the expected color range: colorless, white, gray.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: acicular, crystalline, massive.

Often confused with

Kernite vs. its common look-alikes, and how to tell them apart in the field.

Often found alongside kernite

Minerals reported to co-occur with kernite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Na₂B₄O₆(OH)₂·3H₂O
Mohs hardness: 2.5
Density: 1.906 g/cm³
Colors: Colorless White Gray
Streak: White
Luster: Vitreous, satiny on fibrous cleavages
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Acicular, crystalline, massive
Cleavage: On {100} and {001}, perfect; on {102}, fair
Rarity: Uncommon
Uses: Industrial, Collector
Host rock: An important ore mineral of borax in sedimentary borate deposits, deposited under warm conditions or formed by metamorphism

Where rockhounds find kernite

Classic worldwide localities

Kramer borate deposit, Boron, Kern Co., California, USA
Tincalayu borax deposit, Salar del Hombre Muerto, Salta Province, Argentina
Kirka borate deposit, Kütahya Province, Turkey

Field-hunting tip

Where it forms: An important ore mineral of borax in sedimentary borate deposits, deposited under warm conditions or formed by metamorphism. If you start seeing borax, inyoite, ulexite in float, you are in the right ground. Typical habit: acicular, crystalline, massive. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify kernite?+

Mohs hardness is 2.5. Luster: vitreous, satiny on fibrous cleavages. The streak is white. Common colors include colorless, white, gray.

Where is kernite found?+

Notable localities include Kramer borate deposit, Boron, Kern Co., California, USA; Tincalayu borax deposit, Salar del Hombre Muerto, Salta Province, Argentina; Kirka borate deposit, Kütahya Province, Turkey.

What rocks look like kernite?+

Kernite is most often confused with Borax, Ulexite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with kernite?+

Kernite commonly co-occurs with Borax, Inyoite, Ulexite, Colemanite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does kernite form in?+

Where it forms: An important ore mineral of borax in sedimentary borate deposits, deposited under warm conditions or formed by metamorphism. Working float back to the host body is the standard way to chase a fresh occurrence.

What is kernite used for?+

Kernite is used in industrial, collector.

Find kernite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.