Cornetite is an uncommon copper phosphate mineral typically found as deep blue, radiating sprays or crusts in the oxidized zones of copper ore bodies. Collectors look for its vivid, intense blue color and distinctive acicular crystal sprays, often occurring alongside other secondary copper minerals like malachite.
Is this cornetite?
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 cornetite with a known reference. Cornetite sits at Mohs 4-5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Cornetite leaves a pale blue streak.
- 3Read the lusterHold the specimen under a strong light. Cornetite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: dark blue, greenish blue.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular crystals, radiating sprays, globular crusts.
Often confused with
Cornetite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Cornetite leaves pale blue, Azurite leaves light blue; luster reads vitreous on Cornetite and vitreous to dull on Azurite.
How to tell apart: Streak differs — Cornetite leaves pale blue, Chrysocolla leaves white.
How to tell apart: Streak differs — Cornetite leaves pale blue, Pseudomalachite leaves light green.
Often found alongside cornetite
Minerals reported to co-occur with cornetite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₃(PO₄)(OH)₃
- Mohs hardness
- 4-5
- Density
- 4.1 g/cm³
- Colors
- Streak
- Pale Blue
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular Crystals, Radiating Sprays, Globular Crusts
- Cleavage
- Distinct On {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Copper Deposits
- Typical price
- $20-200 thumbnail
Where rockhounds find cornetite
Classic worldwide localities
- Democratic Republic of the Congo
- Zambia
- United States
- Australia
Field-hunting tip
Look in oxidized zones of copper deposits country — that is the host setting where cornetite typically forms. If you start seeing malachite, chrysocolla, pseudomalachite in float, you are in the right ground. Field specimens usually show a acicular crystals, radiating sprays, globular crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find cornetite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
