Borax is a soft, sweet-tasting evaporite mineral that readily dehydrates into tincalconite when exposed to air. Collectors should keep specimens in airtight containers to prevent them from turning into a white, chalky powder.
Is this borax?
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 borax with a known reference. Borax sits at Mohs 2-2.5, 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 to resinous, may be earthy.
- 4Match the color rangeCompare against the expected color range: white, colorless, gray, pale blue, pale green, blue, green, gray white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: massive, prismatic, tabular.
Often confused with
Borax vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside borax
Minerals reported to co-occur with borax. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₂B₄O₇·10H₂O
- Mohs hardness
- 2-2.5
- Density
- 1.715 g/cm³
- Streak
- White
- Luster
- Vitreous to resinous, may be earthy
- Transparency
- Translucent to opaque
- Crystal system
- Monoclinic
- Crystal habit
- Massive, prismatic, tabular
- Cleavage
- {100}, perfect; {110}, less perfect; {010}, in traces
- Rarity
- Common
- Uses
- Industrial, Collector, Chemical reagent
- Host rock
- In evaporite deposits, salt lakes, playas, commonly well-crystallized; as an efflorescence on soils in arid regions
Where rockhounds find borax
1 mapped spotsClassic worldwide localities
- Borax Lake, Lake Co., California, USA
- Searles Lake, San Bernardino Co., California, USA
- Kramer borate deposit, Boron, Kern Co., California, USA
- Furnace Creek and Resting Springs, Death Valley, Inyo Co., California, USA
- Originally collected from a number of salt lakes in the Ladakh district, Kashmir to north of Lhasa, Tibet, China, along the Qinghai Province-Xizang Plateau
- Kirka borate deposit, Kütahya Province, Turkey
Field-hunting tip
Where it forms: In evaporite deposits, salt lakes, playas, commonly well-crystallized; as an efflorescence on soils in arid regions. If you start seeing inyoite, ulexite, colemanite in float, you are in the right ground. Typical habit: massive, prismatic, tabular. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in California. Start trip planning there.
Common questions
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Find borax on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
