Algodonite is a rare copper arsenide mineral that typically forms as massive or granular aggregates with a silvery-white metallic luster. It is most famous for its occurrences in the native copper deposits of the Keweenaw Peninsula in Michigan, where it is often found intergrown with domeykite and native copper.
Is this algodonite?
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 algodonite with a known reference. Algodonite sits at Mohs 3.5-4 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Algodonite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Algodonite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: silver-white, steel-gray.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: massive, granular, or botryoidal forms.
Often confused with
Algodonite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Algodonite leaves white, Domeykite leaves metallic white.
How to tell apart: Streak differs — Algodonite leaves white, Koutekite leaves black.
How to tell apart: Streak differs — Algodonite leaves white, Silver leaves silver-white.
Often found alongside algodonite
Minerals reported to co-occur with algodonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₆As
- Mohs hardness
- 3.5-4
- Density
- 8.38 g/cm³
- Colors
- Streak
- White
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Hexagonal
- Crystal habit
- Massive, Granular, Or Botryoidal Forms
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Ore
- Host rock
- Hydrothermal Veins in Copper Deposits
- Typical price
- $20-150 per specimen depending on size and association
Where rockhounds find algodonite
Classic worldwide localities
- Michigan, USA
- Chile
- Bolivia
- Germany
Field-hunting tip
Look in hydrothermal veins in copper deposits country — that is the host setting where algodonite typically forms. If you start seeing domeykite, copper, silver in float, you are in the right ground. Field specimens usually show a massive, granular, or botryoidal forms habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify algodonite?+
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Find algodonite on the map
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