Ojuelaite is a rare secondary mineral typically found as delicate, needle-like acicular crystals forming attractive radial sprays. It is most famous for its occurrence in the Ojuela Mine, where it often forms as a coating or crust in oxidized arsenic-rich environments.
Is this ojuelaite?
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 ojuelaite with a known reference. Ojuelaite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: silky to vitreous.
- 4Match the color rangeCompare against the expected color range: greenish yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular or fibrous radial sprays.
Often confused with
Ojuelaite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads silky to vitreous on Ojuelaite and vitreous on Koninckite.
How to tell apart: Streak differs, so Ojuelaite leaves pale yellow, Scorodite leaves greenish white; luster reads silky to vitreous on Ojuelaite and vitreous to subadamantine, subresinous on Scorodite.
Often found alongside ojuelaite
Minerals reported to co-occur with ojuelaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- ZnFe³⁺₂(AsO₄)₂ (OH)₂·4H₂O
- Mohs hardness
- 3
- Density
- 3.39 g/cm³
- Colors
- Streak
- Pale yellow
- Luster
- Silky to vitreous
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular or fibrous radial sprays
- Cleavage
- On {010}, observable
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare mineral in the oxidized zone of arsenic-rich polymetallic hydrothermal ore deposits
Where rockhounds find ojuelaite
Classic worldwide localities
- Sterling Hill, Ogdensburg, New Jersey, USA
- Ojuela mine, Mapimí, Durango, and at Pitiquito, Sonora, Mexico
- Tsumeb, Namibia
Field-hunting tip
Where it forms: A rare mineral in the oxidized zone of arsenic-rich polymetallic hydrothermal ore deposits. If you start seeing paradamite, scorodite, smithsonite in float, you are in the right ground. Typical habit: acicular or fibrous radial sprays. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ojuelaite?+
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What rocks look like ojuelaite?+
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Find ojuelaite on the map
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