Coulsonite is a rare vanadium-rich member of the spinel group, typically found in metamorphosed iron deposits or as an accessory mineral in mafic rocks. It is physically similar to magnetite and often requires analytical testing for definitive identification due to its dark, non-descript appearance. Collectors seek it primarily as a rare end-member mineral from classic iron-ore localities.
Is this coulsonite?
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 coulsonite with a known reference. Coulsonite sits at Mohs 5.5-6.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Coulsonite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Coulsonite typically shows a submetallic luster.
- 4Match the color rangeCompare against the expected color range: black, dark gray.
- 5Look at form & habitCrystal system: cubic. Typical habit: octahedral, massive, granular.
Often confused with
Coulsonite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Luster reads submetallic on Coulsonite and metallic on Magnetite.
How to tell apart: Streak differs — Coulsonite leaves black, Chromite leaves dark brown.
How to tell apart: Streak differs — Coulsonite leaves black, Franklinite leaves reddish-brown; luster reads submetallic on Coulsonite and metallic on Franklinite.
Often found alongside coulsonite
Minerals reported to co-occur with coulsonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- FeV₂O₄
- Mohs hardness
- 5.5-6.5
- Density
- 4.9-5.1 g/cm³
- Streak
- Black
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Octahedral, Massive, Granular
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Geological Study
- Host rock
- Metamorphic Iron Formations, Igneous Mafic Rocks
- Typical price
- $20-150 per specimen
Where rockhounds find coulsonite
Classic worldwide localities
- California, USA
- Quebec, Canada
- Bushveld Complex, South Africa
Field-hunting tip
Look in metamorphic iron formations, igneous mafic rocks country — that is the host setting where coulsonite typically forms. If you start seeing magnetite, hematite, ilmenite in float, you are in the right ground. Field specimens usually show a octahedral, massive, granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find coulsonite on the map
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