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. Borax leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Borax typically shows a vitreous to earthy luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, gray, pale blue, pale green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic, massive, or encrustations.
Often confused with
Borax vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads vitreous to earthy on Borax and silky on Ulexite.
How to tell apart: Luster reads vitreous to earthy on Borax and dull on Priceite.
How to tell apart: Luster reads vitreous to earthy on Borax and vitreous to pearly on Kernite.
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
- 1.7 g/cm³
- Streak
- White
- Luster
- Vitreous to Earthy
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic, Massive, Or Encrustations
- Cleavage
- Perfect in One Direction
- Fluorescence
- Bright Yellow or Green Under LW UV
- Rarity
- Common
- Uses
- Industrial, Collector, Chemical Reagent
- Host rock
- Evaporite Deposits in Arid Alkaline Lake Beds
- Typical price
- $5-30 for thumbnail specimens
Where rockhounds find borax
1 mapped spotsClassic worldwide localities
- Boron, California, USA
- Searles Lake, California, USA
- Tibet
- Turkey
- Argentina
Field-hunting tip
Look in evaporite deposits in arid alkaline lake beds country, the host setting where borax typically forms. If you start seeing halite, gypsum, kernite in float, you are in the right ground. Field specimens usually show a prismatic, massive, or encrustations habit, so 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.
