Whitecapsite is a rare hydrated iron arsenite mineral originally discovered at the White Caps Mine in Nevada. It typically forms as small, bright yellow transparent crystals or thin crusts associated with arsenic-rich sulfide deposits.
Is this whitecapsite?
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 whitecapsite with a known reference. Whitecapsite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Whitecapsite leaves a pale yellow streak.
- 3Read the lusterHold the specimen under a strong light. Whitecapsite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellow-orange.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: tabular crystals, crystalline crusts.
Often confused with
Whitecapsite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Whitecapsite leaves pale yellow, Pharmacosiderite leaves white; luster reads vitreous on Whitecapsite and adamantine on Pharmacosiderite.
How to tell apart: Scorodite is the harder of the two (Mohs 3.5-4 vs. 2); streak differs, so Whitecapsite leaves pale yellow, Scorodite leaves white; luster reads vitreous on Whitecapsite and vitreous to sub-adamantine on Scorodite.
Often found alongside whitecapsite
Minerals reported to co-occur with whitecapsite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- H₄Fe₂³⁺(AsO₃)₄·4H₂O
- Mohs hardness
- 2
- Density
- 2.16 g/cm³
- Colors
- Streak
- Pale Yellow
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Tabular Crystals, Crystalline Crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins in Sedimentary Rocks
- Typical price
- $50-300 per specimen
Where rockhounds find whitecapsite
Classic worldwide localities
- White Caps Mine, Manhattan, Nevada, USA
Field-hunting tip
Look in hydrothermal veins in sedimentary rocks country, the host setting where whitecapsite typically forms. If you start seeing arsenopyrite, realgar, orpiment in float, you are in the right ground. Field specimens usually show a tabular crystals, crystalline crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find whitecapsite on the map
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