Ulexite is famous for its fiber-optic properties, which allow it to transmit images from one side of a cut piece to the other, earning it the nickname 'TV Rock'. It typically forms as soft, white, cotton-like masses in evaporite basins and is highly sensitive to humidity, often dehydrating and becoming opaque if not stored properly.
Is this ulexite?
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 ulexite with a known reference. Ulexite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Ulexite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Ulexite typically shows a silky luster.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: triclinic. Typical habit: fibrous, acicular, rounded nodules.
Often confused with
Ulexite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside ulexite
Minerals reported to co-occur with ulexite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaCaB₅O₆(OH)₆·5H₂O
- Mohs hardness
- 2.5
- Density
- 1.96 g/cm³
- Streak
- White
- Luster
- Silky
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Fibrous, Acicular, Rounded Nodules
- Cleavage
- Perfect in One Direction
- Fluorescence
- Bright Yellow Under SW UV
- Rarity
- Common
- Uses
- Collector, Scientific Research
- Host rock
- Evaporite Deposits in Arid Salt Pans
- Typical price
- $5-30 for small pieces, $50+ for large polished specimens
Where rockhounds find ulexite
3 mapped spotsClassic worldwide localities
- Boron, California, USA
- Tarapaca, Chile
- Sijilmasa, Morocco
- Argentina
Field-hunting tip
Look in evaporite deposits in arid salt pans country, the host setting where ulexite typically forms. If you start seeing borax, kernite, halite in float, you are in the right ground. Field specimens usually show a fibrous, acicular, rounded nodules habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Oklahoma, Nevada. Start trip planning there.
Common questions
How do you identify ulexite?+
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Can I find ulexite in the United States?+
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Find ulexite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
