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. Ojuelaite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Ojuelaite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, orange-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: Streak differs — Ojuelaite leaves yellow, Koninckite leaves white.
How to tell apart: Streak differs — Ojuelaite leaves yellow, Scorodite leaves white; luster reads vitreous on Ojuelaite and vitreous to sub-adamantine 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
- 3.32 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular or Fibrous Radial Sprays
- Cleavage
- Perfect On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Hydrothermal Zones in Limestone
- Typical price
- $50-300 per specimen depending on size and quality
Where rockhounds find ojuelaite
Classic worldwide localities
- Ojuela Mine, Mapimí, Mexico
- Gold Hill, Utah, USA
Field-hunting tip
Look in oxidized hydrothermal zones in limestone country — that is the host setting where ojuelaite typically forms. If you start seeing arseniosiderite, duftite, adamite in float, you are in the right ground. Field specimens usually show a acicular or fibrous radial sprays habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find ojuelaite on the map
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