Mathiasite is a rare titanium-rich mineral member of the crichtonite group typically found within kimberlite pipes. It presents as small, black, opaque crystals that are often difficult to distinguish from other accessory oxides without analytical testing. Collectors generally find these in association with heavy minerals concentrated during diamond mining operations.
Is this mathiasite?
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 mathiasite with a known reference. Mathiasite sits at Mohs 7.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: gray.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: trigonal. Typical habit: tabular to rhombohedral crystals.
Often confused with
Mathiasite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Mathiasite is noticeably harder (Mohs 7.5 vs. 5-6); streak differs, so Mathiasite leaves gray, Ilmenite leaves black to reddish brown.
How to tell apart: Mathiasite is noticeably harder (Mohs 7.5 vs. 5.5); streak differs, so Mathiasite leaves gray, Chromite leaves brown.
How to tell apart: Mathiasite is noticeably harder (Mohs 7.5 vs. 4.5-5); streak differs, so Mathiasite leaves gray, Crichtonite leaves dark gray.
Often found alongside mathiasite
Minerals reported to co-occur with mathiasite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (K,Ba,Sr)(Zr,Fe)(Mg,Fe)₂(Ti,Cr,Fe)₁₈O₃₈
- Mohs hardness
- 7.5
- Density
- 4.6 g/cm³
- Colors
- Streak
- Gray
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Tabular to rhombohedral crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A primary mantle-derived phase found in heavy-mineral concentrates from metasomatized kimberlite (South Africa)
Where rockhounds find mathiasite
Classic worldwide localities
- Jagersfontein diamond mine, Free State, and the Bultfontein diamond mine and Kolonkwanen kimberlite prospect, Mackenzie’s Post district, Cape Province, South Africa
Field-hunting tip
Where it forms: A primary mantle-derived phase found in heavy-mineral concentrates from metasomatized kimberlite (South Africa). If you start seeing lindsleyite, olivine, diopside in float, you are in the right ground. Typical habit: tabular to rhombohedral crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify mathiasite?+
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What rocks look like mathiasite?+
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Find mathiasite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
