Juanitaite is a very rare secondary mineral typically found as small, vibrant green square tablets or crusts in oxidized tellurium-bearing deposits. It is best identified under magnification by its characteristic tetragonal plate habit, primarily known from its type locality in Utah. Due to its extreme rarity and complex chemistry, it is a highly sought-after species for advanced mineral collectors.
Is this juanitaite?
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 juanitaite with a known reference. Juanitaite sits at Mohs ~1, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale greenish yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: resinous to dull; reflections from {001} often appear bronzy.
- 4Match the color rangeCompare against the expected color range: olive green, grass green.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: microscopic crystals, square, tabular.
Often confused with
Juanitaite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Mackayite is the harder of the two (Mohs 4.5 vs. ~1); luster reads resinous to dull; reflections from {001} often appear bronzy on Juanitaite and vitreous on Mackayite.
How to tell apart: Emmonsite is the harder of the two (Mohs ~5 vs. ~1); luster reads resinous to dull; reflections from {001} often appear bronzy on Juanitaite and vitreous on Emmonsite.
Often found alongside juanitaite
Minerals reported to co-occur with juanitaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Cu,Ca,Fe)₁₀Bi(AsO₄)₄(OH)₁₁·2H₂O
- Mohs hardness
- ~1
- Density
- 3.61 g/cm³
- Colors
- Streak
- Pale greenish yellow
- Luster
- Resinous to dull; reflections from {001} often appear bronzy
- Transparency
- Translucent
- Crystal system
- Tetragonal
- Crystal habit
- Microscopic crystals, square, tabular
- Cleavage
- Perfect on {001} and {110}, good on {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral from the oxidation of tennantite, chalcopyrite, and pyrite in quartz veins
Where rockhounds find juanitaite
Classic worldwide localities
- Gold Hill mine, Tooele County, Utah, USA (type locality)
Field-hunting tip
Where it forms: A secondary mineral from the oxidation of tennantite, chalcopyrite, and pyrite in quartz veins. If you start seeing mixite, conichalcite, connellite in float, you are in the right ground. Typical habit: microscopic crystals, square, tabular. Train your eye for that shape before scanning the outcrop.
Common questions
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Find juanitaite on the map
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