Hydroboracite is an uncommon borate mineral typically found as delicate, fibrous, or acicular white masses within evaporite basins. Collectors often look for it as part of mineral assemblages in desert regions, where it forms distinct, needle-like spray habits that are prized for their aesthetic quality.
Is this hydroboracite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch hydroboracite with a known reference. Hydroboracite sits at Mohs 2-6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous, silky if fibrous.
- 4Match the color rangeCompare against the expected color range: white, colorless, greenish, light brown, wine yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous, foliated.
Often confused with
Hydroboracite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside hydroboracite
Minerals reported to co-occur with hydroboracite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaMgB₆O₁₁·6H₂O
- Mohs hardness
- 2-6
- Density
- 2.15-2.17 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous, silky if fibrous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous, foliated
- Cleavage
- {010}, perfect; {100}, distinct
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- Typically formed by groundwater alteration of colemanite; may be primary
Where rockhounds find hydroboracite
Classic worldwide localities
- Thompson mine, near Ryan, in the Terry deposit, and at the Eagle Borax Spring, Furnace Creek district, Death Valley, Inyo Co., in the Kramer borate deposit, Boron, Kern Co., California, USA
- Originally described from an unknown locality in the “Caucasus”, at that time a general name for the areas south of European Russia
- Inder boron deposit, Kazakhstan
- Niedersachswerfen anhydrite deposit, near Nordhausen, Harz Mountains, Germany
- Potash Corporation of America mine, Penobsquis evaporite deposit, and in the Salt Springs evaporite deposit, near Sussex, New Brunswick, Canada
- Bigadiç borate district, Balıkesir Province, Turkey
Field-hunting tip
Where it forms: Typically formed by groundwater alteration of colemanite; may be primary. If you start seeing colemanite, hydroboracite, tunellite in float, you are in the right ground. Typical habit: fibrous, foliated. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify hydroboracite?+
Where is hydroboracite found?+
What rocks look like hydroboracite?+
What minerals are found with hydroboracite?+
What kind of rock does hydroboracite form in?+
What is hydroboracite used for?+
Find hydroboracite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
