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, so 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, so 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, 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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