Legrandite is a highly sought-after secondary mineral known for its vibrant yellow color and elongated prismatic crystal form. It is most famous for its occurrences at the Ojuela Mine in Mexico, where it forms stunning, sharp radiating sprays of crystals.
Is this legrandite?
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 legrandite with a known reference. Legrandite sits at Mohs 4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: yellow, yellowish-orange.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: crystalline, prismatic.
Often confused with
Legrandite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside legrandite
Minerals reported to co-occur with legrandite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Zn₂(AsO₄)(OH)·H₂O
- Mohs hardness
- 4.5
- Density
- 3.98-4.01 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Crystalline, prismatic
- Cleavage
- Fair to poor on {100}
- Fluorescence
- Bright yellow under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- An uncommon secondary mineral in the oxidized zone of Zn–As-bearing deposits; rare in granite pegmatite
Where rockhounds find legrandite
Classic worldwide localities
- Sterling Hill, Ogdensburg, Sussex Co., New Jersey, USA
- Flor de Peña mine, Lampazos, Nuevo León, Mexico
- Ojuela mine, Mapimí, Durango, Mexico
- Potosí mine, Santa Eulalia, Chihuahua, Mexico
- Tsumeb, Namibia
- Ogibira mine, near Osa, Okayama Prefecture, and the Toroku mine, Miyazaki Prefecture, Japan
Field-hunting tip
Where it forms: An uncommon secondary mineral in the oxidized zone of Zn–As-bearing deposits; rare in granite pegmatite. If you start seeing adamite, paradamite, köttigite in float, you are in the right ground. Typical habit: crystalline, prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify legrandite?+
Where is legrandite found?+
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Find legrandite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
