Bentorite is a very rare member of the ettringite group typically found as small, delicate, pinkish-violet prismatic crystals. It is primarily known from its type locality in the Hatrurim Basin of Israel, occurring in high-temperature metamorphic environments. Due to its softness and high water content, specimens should be handled with care and stored in a low-humidity environment.
Is this bentorite?
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 bentorite with a known reference. Bentorite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Bentorite leaves a very pale violet streak.
- 3Read the lusterHold the specimen under a strong light. Bentorite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: pink, violet, white.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: prismatic crystals.
Often confused with
Bentorite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Bentorite leaves very pale violet, Ettringite leaves white.
How to tell apart: Thaumasite is the harder of the two (Mohs 3.5 vs. 2); streak differs, so Bentorite leaves very pale violet, Thaumasite leaves white.
Often found alongside bentorite
Minerals reported to co-occur with bentorite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₆(Cr,Al)₂(SO₄)₃(OH)₁₂·26H₂O
- Mohs hardness
- 2
- Density
- 2.025 g/cm³
- Streak
- Very Pale Violet
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Hexagonal
- Crystal habit
- Prismatic Crystals
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphic Rocks of The Hatrurim Formation
Where rockhounds find bentorite
1 mapped spotsClassic worldwide localities
- Hatrurim Basin, Israel
Field-hunting tip
Look in metamorphic rocks of the hatrurim formation country, the host setting where bentorite typically forms. If you start seeing calcite, portlandite, hydrocalumite in float, you are in the right ground. Field specimens usually show a prismatic crystals habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah. Start trip planning there.
Common questions
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Find bentorite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
