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 — Oldhamite leaves white, Galena leaves lead-gray; luster reads dull on Oldhamite and metallic on Galena.
How to tell apart: Streak differs — 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 — that is 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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