Colusite is a rare copper-vanadium-arsenic sulfosalt often found as fine-grained masses within hydrothermal copper ore deposits. It is best identified in polished section under reflected light by its distinctive bronze-brown color and association with other complex sulfides.
Is this colusite?
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 colusite with a known reference. Colusite sits at Mohs 3-4, 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: bronze.
- 5Look at form & habitCrystal system: cubic. Typical habit: massive.
Often confused with
Colusite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Colusite leaves black, Tennantite leaves reddish gray.
How to tell apart: Streak differs, so Colusite leaves black, Enargite leaves grayish black.
How to tell apart: Streak differs, so Colusite leaves black, Germanite leaves dark gray to black.
Often found alongside colusite
Minerals reported to co-occur with colusite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₂₆V₂As₆S₃₂
- Mohs hardness
- 3-4
- Density
- 4.2 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Massive
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- Widespread in small amounts with other sulfides and sulfosalts, typically in hydrothermal vein and disseminated copper deposits
Where rockhounds find colusite
Classic worldwide localities
- Leonard mine (type locality) and other mines, Butte, Silver Bow Co., Montana, USA
- Magma mine, Superior, Pinal Co., and the Campbell mine, Bisbee, Cochise Co., Arizona, USA
- Red Mountain Pass, San Juan, Ouray Co., and in the Buffalo Boy mine, near Silverton, San Juan Co., Colorado, USA
- Kidd Creek mine, near Timmins, Ontario, Canada
- Chuquicamata, Antofagasta, Chile
- Cerro de Pasco, Peru
Field-hunting tip
Where it forms: Widespread in small amounts with other sulfides and sulfosalts, typically in hydrothermal vein and disseminated copper deposits. If you start seeing pyrite, tetrahedrite–tennantite, enargite in float, you are in the right ground. Typical habit: massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify colusite?+
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Find colusite on the map
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