Gajardoite is a rare potassium calcium arsenic oxide that forms colorless hexagonal plates. Associated minerals include arsenolite, chongite and talmessite. It was first described from Torrecillas mine, northern Atacama Desert, Iquique Province, Tarapacá Region, Chile.
Is this gajardoite?
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 gajardoite with a known reference. Gajardoite sits at Mohs 2-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Gajardoite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Gajardoite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular, pseudo-hexagonal crystals.
Often confused with
Gajardoite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Gajardoite leaves white, Pharmacosiderite leaves yellowish green; luster reads vitreous on Gajardoite and adamantine on Pharmacosiderite.
How to tell apart: Luster reads vitreous on Gajardoite and vitreous to subadamantine on Scorodite.
Often found alongside gajardoite
Minerals reported to co-occur with gajardoite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KCa₀.₅As³⁺₄O₆Cl₂·5H₂O
- Mohs hardness
- 2-3
- Density
- 2.64 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular, Pseudo-hexagonal Crystals
- Cleavage
- Perfect On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins
Where rockhounds find gajardoite
Classic worldwide localities
- Gajardo mine, Chile
Field-hunting tip
Look in hydrothermal veins country, the host setting where gajardoite typically forms. If you start seeing arsenates, quartz in float, you are in the right ground. Field specimens usually show a tabular, pseudo-hexagonal crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find gajardoite on the map
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