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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: submetallic.
- 4Match the color rangeCompare against the expected color range: light brown, dark brown.
- 5Look at form & habitCrystal system: cubic. Typical habit: anhedral grains.
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. 2.5-2.75); streak differs, so Oldhamite leaves white, Galena leaves lead-gray; luster reads submetallic on Oldhamite and metallic on Galena.
How to tell apart: Streak differs, so Oldhamite leaves white, Alabandite leaves dark green.
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
- Submetallic
- Transparency
- Transparent
- Crystal system
- Cubic
- Crystal habit
- Anhedral grains
- Cleavage
- On {001}
- Rarity
- Rare
- Uses
- Scientific research, Collector
- Host rock
- Due to high melting point of 2450°C, an early nebular condensate; may fill the latest interstices between silicates in enstatite chondrite and achondrite meteorites
Where rockhounds find oldhamite
Classic worldwide localities
- Bustee (type locality), Hvittis, Mayo Belwa, Indarch, Kota-Kota, Adhi-Kot, Norton County, Peña Blanca Spring, Abee, Qingzhen, etc., meteorites
Field-hunting tip
Where it forms: Due to high melting point of 2450°C, an early nebular condensate; may fill the latest interstices between silicates in enstatite chondrite and achondrite meteorites. If you start seeing enstatite, augite, niningerite in float, you are in the right ground. Typical habit: anhedral grains. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify oldhamite?+
Where is oldhamite found?+
What rocks look like oldhamite?+
What minerals are found with oldhamite?+
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What is oldhamite used for?+
Find oldhamite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
