Donwilhelmsite is a rare high-pressure mineral discovered in lunar meteorites that formed during impact events on the Moon. It is a structural polymorph of anorthite and typically occurs as microscopic inclusions within impact-melted breccias.
Is this donwilhelmsite?
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 donwilhelmsite with a known reference. Donwilhelmsite sits at Mohs not determined — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Donwilhelmsite leaves a not determined streak.
- 3Read the lusterHold the specimen under a strong light. Donwilhelmsite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: dark brown, black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: anhedral grains.
Often confused with
Donwilhelmsite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside donwilhelmsite
Minerals reported to co-occur with donwilhelmsite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaAl₂Si₂O₈
- Mohs hardness
- not determined
- Density
- 4.15 g/cm³
- Colors
- Streak
- Not Determined
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Anhedral Grains
- Cleavage
- Not Determined
- Rarity
- Rare
- Uses
- Scientific Research
- Host rock
- Lunar Impact Melt
- Typical price
- n/a
Where rockhounds find donwilhelmsite
Classic worldwide localities
- Dhofar 025 meteorite
- Lunar meteorites
Field-hunting tip
Look in lunar impact melt country — that is the host setting where donwilhelmsite typically forms. If you start seeing olivine, pyroxene, maskelynite in float, you are in the right ground. Field specimens usually show a anhedral grains habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find donwilhelmsite on the map
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