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 5.5-6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Plancheite leaves a light blue streak.
- 3Read the lusterHold the specimen under a strong light. Plancheite typically shows a silky luster.
- 4Match the color rangeCompare against the expected color range: blue, light blue, dark blue, greenish-blue.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: botryoidal, fibrous, acicular aggregates.
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 5.5-6 vs. 2-4); streak differs, so Plancheite leaves light blue, Chrysocolla leaves white; luster reads silky on Plancheite and vitreous on Chrysocolla.
How to tell apart: Streak differs, so Plancheite leaves light blue, Hemimorphite leaves white; luster reads silky on Plancheite and vitreous on Hemimorphite.
How to tell apart: Plancheite is noticeably harder (Mohs 5.5-6 vs. 3.5-4); luster reads silky on Plancheite and vitreous to dull 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
- 5.5-6
- Density
- 3.37 g/cm³
- Streak
- Light Blue
- Luster
- Silky
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Botryoidal, Fibrous, Acicular Aggregates
- Cleavage
- Good
- Rarity
- Uncommon
- Uses
- Collector, Decorative
- Host rock
- Oxidized Zones of Copper Ore Deposits
- Typical price
- $15-150 thumbnail, $50-400 cabinet
Where rockhounds find plancheite
Classic worldwide localities
- Katanga Copper Crescent (DR Congo)
- Namibia
- Arizona (USA)
Field-hunting tip
Look in oxidized zones of copper ore deposits country, the host setting where plancheite typically forms. If you start seeing chrysocolla, malachite, dioptase in float, you are in the right ground. Field specimens usually show a botryoidal, fibrous, acicular aggregates habit, so 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.
