Plancheite is a beautiful, distinctively fibrous copper silicate that often forms stunning botryoidal or tufted masses. Collectors prize it for its vibrant sky-blue to deep-blue coloration and its association with other secondary copper minerals in oxidized ore zones.
Is this plancheite?
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 plancheite with a known reference. Plancheite sits at Mohs 6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: light blue.
- 3Read the lusterHold the specimen under a strong light. Luster: satiny.
- 4Match the color rangeCompare against the expected color range: blue, light blue, dark blue, greenish-blue.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular, fibrous, radial.
Often confused with
Plancheite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Plancheite is noticeably harder (Mohs 6 vs. ~2-4); streak differs, so Plancheite leaves light blue, Chrysocolla leaves white when pure; luster reads satiny on Plancheite and vitreous, porcelaneous, earthy on Chrysocolla.
How to tell apart: Plancheite is noticeably harder (Mohs 6 vs. 4.5-5); streak differs, so Plancheite leaves light blue, Hemimorphite leaves white; luster reads satiny on Plancheite and vitreous, subpearly, adamantine, rarely silky on Hemimorphite.
How to tell apart: Plancheite is noticeably harder (Mohs 6 vs. 3.5-4); streak differs, so Plancheite leaves light blue, Azurite leaves pale blue; luster reads satiny on Plancheite and vitreous to subadamantine on Azurite.
Often found alongside plancheite
Minerals reported to co-occur with plancheite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₈Si₈O₂₂(OH)₄·H₂O
- Mohs hardness
- 6
- Density
- 3.65-3.80 g/cm³
- Streak
- Light blue
- Luster
- Satiny
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular, fibrous, radial
- Cleavage
- Good
- Rarity
- Uncommon
- Uses
- Collector, Decorative
- Host rock
- A rare secondary mineral in the oxidized portion of copper deposits
Where rockhounds find plancheite
Classic worldwide localities
- Table Mountain mine, Galiuro Mountains, and the Azurite mine, Tortolita Mountains, Pinal Co., Arizona, USA
- Bighorn district, south of Aguila, Maricopa Co., Arizona, USA
- Harquehala Mountains, Yuma Co., Arizona, USA
- Arizona, USA
- Mindouli, Renéville, and Tshiniama, Congo Republic
- Congo (Zaire), Tantara, Mindigi, and M'sesa, near Kambove, Katanga (Shaba) Province
Field-hunting tip
Where it forms: A rare secondary mineral in the oxidized portion of copper deposits. If you start seeing chrysocolla, dioptase, malachite in float, you are in the right ground. Typical habit: acicular, fibrous, radial. Train your eye for that shape before scanning the outcrop.
Common questions
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Find plancheite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
