Nissonite is a rare copper-magnesium phosphate that typically forms as delicate, thin blue-green platy crystals or crusts in oxidized zones of copper deposits. Collectors should look for it as small, fragile coatings within vugs alongside other secondary copper minerals. It is highly valued for its distinct color and rarity, usually appearing as microscopic specimens.
Is this nissonite?
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 nissonite with a known reference. Nissonite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: light green.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: bluish green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, crusts, radial aggregates.
Often confused with
Nissonite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Nissonite leaves light green, Vauquelinite leaves greenish to brownish; luster reads vitreous on Nissonite and adamantine to resinous on Vauquelinite.
How to tell apart: Streak differs, so Nissonite leaves light green, Torbernite leaves pale green.
Often found alongside nissonite
Minerals reported to co-occur with nissonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CuMg(PO₄)(OH)·2.5H₂O
- Mohs hardness
- 2.5
- Density
- 2.73 g/cm³
- Colors
- Streak
- Light green
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Platy crystals, crusts, radial aggregates
- Cleavage
- {100}, fair
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A very rare mineral in a copper prospect (Panoche Valley, California, USA); in a Precambrian sedimentary iron deposit (Iron Monarch quarry, Australia)
Where rockhounds find nissonite
Classic worldwide localities
- Llanada copper mine, 4 miles NNE of Llanada, San Benito Co., California (type locality)
Field-hunting tip
Where it forms: A very rare mineral in a copper prospect (Panoche Valley, California, USA); in a Precambrian sedimentary iron deposit (Iron Monarch quarry, Australia). If you start seeing malachite, azurite, libethenite in float, you are in the right ground. Typical habit: platy crystals, crusts, radial aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify nissonite?+
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Find nissonite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
