Esperanzaite is a rare secondary arsenate mineral found in hydrothermal tin deposits. It typically forms small, clear to yellowish tabular crystals or radiating sprays on a matrix of host ore minerals.
Is this esperanzaite?
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 esperanzaite with a known reference. Esperanzaite 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: blue green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: botryoidal, spherical.
Often confused with
Esperanzaite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Esperanzaite is noticeably harder (Mohs 4.5 vs. 2.5); streak differs, so Esperanzaite leaves white, Pharmacosiderite leaves yellowish green; luster reads vitreous on Esperanzaite and adamantine to greasy on Pharmacosiderite.
How to tell apart: Streak differs, so Esperanzaite leaves white, Scorodite leaves greenish white.
Often found alongside esperanzaite
Minerals reported to co-occur with esperanzaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaCa₂Al₂(AsO₄)₂F₄(OH)·2H₂O
- Mohs hardness
- 4.5
- Density
- 3.24 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Botryoidal, spherical
- Cleavage
- Perfect on {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Very rare from a tin-bearing rhyolite
Where rockhounds find esperanzaite
Classic worldwide localities
- La Esperanza mine, 3.7 km southeast of Madero, Zaragosa district, Durango, Mexico
Field-hunting tip
Where it forms: Very rare from a tin-bearing rhyolite. If you start seeing hematite, cassiterite, quartz in float, you are in the right ground. Typical habit: botryoidal, spherical. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify esperanzaite?+
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Find esperanzaite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
