Tangdanite is a rare hydrated copper phosphate mineral typically found as small tabular blue to blue-green crystals in oxidized zones of copper deposits. It was first described from the Tangdan Mine in China and is highly prized by micromounters and advanced mineral collectors for its vibrant color.
Is this tangdanite?
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 tangdanite with a known reference. Tangdanite sits at Mohs 2-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Tangdanite leaves a light green streak.
- 3Read the lusterHold the specimen under a strong light. Tangdanite typically shows a pearly to silky luster.
- 4Match the color rangeCompare against the expected color range: blue, green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, crusts, pulverulent aggregates.
Often confused with
Tangdanite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Turquoise is the harder of the two (Mohs 5-6 vs. 2-3); streak differs, so Tangdanite leaves light green, Turquoise leaves white; luster reads pearly to silky on Tangdanite and vitreous to dull to waxy on Turquoise.
How to tell apart: Libethenite is the harder of the two (Mohs 4 vs. 2-3); streak differs, so Tangdanite leaves light green, Libethenite leaves pale green; luster reads pearly to silky on Tangdanite and vitreous on Libethenite.
How to tell apart: Pseudomalachite is the harder of the two (Mohs 4-4.5 vs. 2-3); luster reads pearly to silky on Tangdanite and vitreous on Pseudomalachite.
Often found alongside tangdanite
Minerals reported to co-occur with tangdanite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂Cu₉(AsO₄)₄(SO₄)₀.₅(OH)₉·9H₂O
- Mohs hardness
- 2-3
- Density
- 3.32 g/cm³
- Streak
- Light Green
- Luster
- Pearly to Silky
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular Crystals, Crusts, Pulverulent Aggregates
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Copper-bearing Hydrothermal Deposits
Where rockhounds find tangdanite
Classic worldwide localities
- Tangdan Mine, Dongchuan District, China
- Chuquicamata Mine, Chile
Field-hunting tip
Look in oxidized copper-bearing hydrothermal deposits country, the host setting where tangdanite typically forms. If you start seeing malachite, azurite, chrysocolla in float, you are in the right ground. Field specimens usually show a tabular crystals, crusts, pulverulent aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find tangdanite on the map
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