Hawthorneite is an extremely rare barium chromium titanium oxide primarily found within kimberlitic or ultra-alkaline rock matrices. Collectors typically look for small, black, hexagonal tabular crystals that exhibit a metallic luster under bright light.
Is this hawthorneite?
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 hawthorneite with a known reference. Hawthorneite sits at Mohs ~5.8, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: black, brown.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: granular, inclusions.
Often confused with
Hawthorneite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Hawthorneite leaves black, Magnetoplumbite leaves dark brown.
How to tell apart: Hawthorneite is noticeably harder (Mohs ~5.8 vs. 4.5-5); streak differs, so Hawthorneite leaves black, Crichtonite leaves dark gray.
Often found alongside hawthorneite
Minerals reported to co-occur with hawthorneite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- BaMgTi₃Cr₄Fe₂Fe₂O₁₉
- Mohs hardness
- ~5.8
- Density
- 5.02 g/cm³
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Hexagonal
- Crystal habit
- Granular, inclusions
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Formed during upper-mantle (75–100 km, 900–1100°C, 20–30 kbar) metasomatism of chromian spinel in peridotite xenoliths in a kimberlite pipe
Where rockhounds find hawthorneite
Classic worldwide localities
- Bultfontein diamond mine, Kimberley, Cape Province, South Africa
Field-hunting tip
Where it forms: Formed during upper-mantle (75–100 km, 900–1100°C, 20–30 kbar) metasomatism of chromian spinel in peridotite xenoliths in a kimberlite pipe. If you start seeing olivine, enstatite, phlogopite in float, you are in the right ground. Typical habit: granular, inclusions. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify hawthorneite?+
Where is hawthorneite found?+
What rocks look like hawthorneite?+
What minerals are found with hawthorneite?+
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What is hawthorneite used for?+
Find hawthorneite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
