Gerhardtite is a rare copper nitrate mineral typically found in arid regions as an oxidation product of copper deposits. It is recognized by its vibrant emerald-green color and thin, platy crystals that often form crusts or delicate clusters.
Is this gerhardtite?
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 gerhardtite with a known reference. Gerhardtite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Gerhardtite leaves a light green streak.
- 3Read the lusterHold the specimen under a strong light. Gerhardtite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: emerald-green, dark green, yellow-green.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: tabular crystals, sometimes elongated or pseudo-hexagonal; also occurs in crusts or granular aggregates.
Often confused with
Gerhardtite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Malachite is the harder of the two (Mohs 3.5-4 vs. 2).
How to tell apart: Atacamite is the harder of the two (Mohs 3-3.5 vs. 2); streak differs — Gerhardtite leaves light green, Atacamite leaves apple green; luster reads vitreous on Gerhardtite and adamantine to vitreous on Atacamite.
How to tell apart: Libethenite is the harder of the two (Mohs 4 vs. 2); streak differs — Gerhardtite leaves light green, Libethenite leaves pale green.
Often found alongside gerhardtite
Minerals reported to co-occur with gerhardtite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₂NO₃(OH)₃
- Mohs hardness
- 2
- Density
- 3.4 g/cm³
- Streak
- Light Green
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Tabular Crystals, Sometimes Elongated or Pseudo-hexagonal; Also Occurs in Crusts or Granular Aggregates
- Cleavage
- Perfect On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Copper Ore Deposits
- Typical price
- $50-500 thumbnail
Where rockhounds find gerhardtite
Classic worldwide localities
- Likasi, DR Congo
- Bisbee, Arizona, USA
- Chile
- New Caledonia
Field-hunting tip
Look in oxidized zones of copper ore deposits country — that is the host setting where gerhardtite typically forms. If you start seeing malachite, chrysocolla, azurite in float, you are in the right ground. Field specimens usually show a tabular crystals, sometimes elongated or pseudo-hexagonal; also occurs in crusts or granular aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find gerhardtite on the map
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