Luddenite is a rare lead-copper silicate mineral typically found as delicate, pale green platy crystals or radiating sprays. It is predominantly known from the Mammoth-Saint Anthony Mine in Tiger, Arizona, where it occurs as a secondary mineral in oxidized ore zones.
Is this luddenite?
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 luddenite with a known reference. Luddenite sits at Mohs 4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: slightly paler nickel green.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly.
- 4Match the color rangeCompare against the expected color range: nickel green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: aggregates, fan shaped, rosette.
Often confused with
Luddenite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Luddenite leaves slightly paler nickel green, Chrysocolla leaves white when pure; luster reads pearly on Luddenite and vitreous, porcelaneous, earthy on Chrysocolla.
How to tell apart: Dioptase is the harder of the two (Mohs 5 vs. 4); streak differs, so Luddenite leaves slightly paler nickel green, Dioptase leaves green; luster reads pearly on Luddenite and vitreous on Dioptase.
Often found alongside luddenite
Minerals reported to co-occur with luddenite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₂Pb₂Si₅O₁₄·14H₂O
- Mohs hardness
- 4
- Density
- 4.45 g/cm³
- Colors
- Nickel green
- Streak
- Slightly paler nickel green
- Luster
- Pearly
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Aggregates, fan shaped, rosette
- Cleavage
- Parallel and normal to the plane of flattening of the microcrystals
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In thoroughly oxidized Pb{Cu sulfide ores
Where rockhounds find luddenite
Classic worldwide localities
- Artillery Peak, Mohave County, Arizona, USA (type locality)
Field-hunting tip
Where it forms: In thoroughly oxidized Pb{Cu sulfide ores. If you start seeing galena, chalcopyrite, fluorite in float, you are in the right ground. Typical habit: aggregates, fan shaped, rosette. Train your eye for that shape before scanning the outcrop.
Common questions
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Find luddenite on the map
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