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 — that is 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.
