Diaspore is an aluminum oxide hydroxide mineral known for its excellent cleavage and occasional color-changing properties in gem-grade material. It typically forms as platy or acicular crystals within bauxite-rich metamorphic rocks or hydrothermal veins. Collectors prize it for its high luster and the distinct pleochroism exhibited by transparent specimens.
Is this diaspore?
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 diaspore with a known reference. Diaspore sits at Mohs 6.5-7, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Diaspore leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Diaspore typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, gray, colorless, yellowish, brownish, violet, greenish.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: platy or needle-like crystals, foliated masses, or massive scales.
Often confused with
Diaspore vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside diaspore
Minerals reported to co-occur with diaspore. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- AlO(OH)
- Mohs hardness
- 6.5-7
- Density
- 3.3-3.5 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Platy or Needle-like Crystals, Foliated Masses, Or Massive Scales
- Cleavage
- Perfect in One Direction
- Rarity
- Uncommon
- Uses
- Gemstone, Collector, Industrial
- Host rock
- Metamorphic Bauxite Deposits, Emery Deposits, And Some Pegmatites
- Typical price
- $20-100 per gram for gem-grade material, $10-50 for mineral specimens
Where rockhounds find diaspore
1 mapped spotsClassic worldwide localities
- Mugla, Turkey
- Ural Mountains, Russia
- Chester, Massachusetts, USA
- Postmasburg, South Africa
- Kremnica, Slovakia
Field-hunting tip
Look in metamorphic bauxite deposits, emery deposits, and some pegmatites country, the host setting where diaspore typically forms. If you start seeing corundum, chlorite, magnetite in float, you are in the right ground. Field specimens usually show a platy or needle-like crystals, foliated masses, or massive scales habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Massachusetts. Start trip planning there.
Common questions
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Find diaspore on the map
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