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 2-2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: strongly vitreous.
- 4Match the color rangeCompare against the expected color range: bright orange, golden-brownish orange.
- 5Look at form & habitCrystal system: hexagonal. 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 yellow, Pharmacosiderite leaves yellowish green; luster reads strongly vitreous on Whitecapsite and adamantine to greasy on Pharmacosiderite.
How to tell apart: Scorodite is the harder of the two (Mohs 3.5-4 vs. 2-2.5); streak differs, so Whitecapsite leaves yellow, Scorodite leaves greenish white; luster reads strongly vitreous on Whitecapsite and vitreous to subadamantine, subresinous 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
- H₁₆Fe₅Fe₁₄Sb₆(AsO₄)₁₈O₁₆·120H₂O
- Mohs hardness
- 2-2.5
- Density
- 2.30 g/cm³
- Colors
- Bright orangeGolden-brownish orange
- Streak
- Yellow
- Luster
- Strongly vitreous
- Transparency
- Transparent
- Crystal system
- Hexagonal
- Crystal habit
- Tabular crystals, crystalline crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral in the oxidation zone of a hydrothermal sulfide deposit containing arsenopyrite, pyrite and stibnite
Where rockhounds find whitecapsite
Classic worldwide localities
- White Caps Mine, Manhattan, Nevada, USA
Field-hunting tip
Where it forms: A secondary mineral in the oxidation zone of a hydrothermal sulfide deposit containing arsenopyrite, pyrite and stibnite. If you start seeing picropharmacolite, guerinite, sulfur in float, you are in the right ground. Typical habit: tabular crystals, crystalline crusts. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify whitecapsite?+
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Find whitecapsite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
