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, so Ojuelaite leaves yellow, Koninckite leaves white.
How to tell apart: Streak differs, so 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, 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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