Oldhamite is an extremely rare calcium sulfide mineral found almost exclusively in meteorites. It typically occurs as tiny, rounded inclusions within enstatite-rich meteorites and is highly unstable in terrestrial conditions, easily decomposing when exposed to moisture.
Is this oldhamite?
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 oldhamite with a known reference. Oldhamite sits at Mohs 4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Oldhamite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Oldhamite typically shows a dull luster.
- 4Match the color rangeCompare against the expected color range: yellowish-brown, brown, gray.
- 5Look at form & habitCrystal system: cubic. Typical habit: massive, rounded grains, rarely cubic.
Often confused with
Oldhamite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Oldhamite is noticeably harder (Mohs 4 vs. 2.5); streak differs, so Oldhamite leaves white, Galena leaves lead-gray; luster reads dull on Oldhamite and metallic on Galena.
How to tell apart: Streak differs, so Oldhamite leaves white, Alabandite leaves dark green to olive-green; luster reads dull on Oldhamite and submetallic to dull on Alabandite.
Often found alongside oldhamite
Minerals reported to co-occur with oldhamite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaS
- Mohs hardness
- 4
- Density
- 2.58 g/cm³
- Colors
- Streak
- White
- Luster
- Dull
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Massive, Rounded Grains, Rarely Cubic
- Cleavage
- Perfect Cubic
- Rarity
- Rare
- Uses
- Scientific Research, Collector
- Host rock
- Enstatite Achondrites (aubrites) and Enstatite Chondrites
- Typical price
- $200-2000+ depending on meteorite specimen size
Where rockhounds find oldhamite
Classic worldwide localities
- Bustee meteorite, India
- Norton County meteorite, USA
- Kaidun meteorite, Yemen
Field-hunting tip
Look in enstatite achondrites (aubrites) and enstatite chondrites country, the host setting where oldhamite typically forms. If you start seeing enstatite, diopside, kamacite in float, you are in the right ground. Field specimens usually show a massive, rounded grains, rarely cubic habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find oldhamite on the map
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