Zýkaite is a rare secondary iron arsenate sulfate typically found as encrustations or botryoidal masses in the oxidized zones of ore deposits. It is named in honor of Czech chemist Václav Zýka and is primarily sought by advanced mineral collectors specializing in rare supergene minerals.
Is this zýkaite?
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 zýkaite with a known reference. Zýkaite sits at Mohs 2.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Zýkaite leaves a pale yellow streak.
- 3Read the lusterHold the specimen under a strong light. Zýkaite typically shows a dull luster.
- 4Match the color rangeCompare against the expected color range: green, yellow-green, brown.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: botryoidal, crusts, or radial aggregates.
Often confused with
Zýkaite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Scorodite is the harder of the two (Mohs 3.5-4 vs. 2.5); streak differs — Zýkaite leaves pale yellow, Scorodite leaves white; luster reads dull on Zýkaite and vitreous to sub-adamantine on Scorodite.
How to tell apart: Streak differs — Zýkaite leaves pale yellow, Pitticite leaves yellowish; luster reads dull on Zýkaite and resinous on Pitticite.
Often found alongside zýkaite
Minerals reported to co-occur with zýkaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe³⁺₄(AsO₄)₃(SO₄)(OH)·15H₂O
- Mohs hardness
- 2.5
- Density
- 2.68 g/cm³
- Colors
- Streak
- Pale Yellow
- Luster
- Dull
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Botryoidal, Crusts, Or Radial Aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Arsenic-rich Hydrothermal Veins
- Typical price
- $20-150 thumbnail specimens
Where rockhounds find zýkaite
Classic worldwide localities
- Jáchymov, Czech Republic
- Kutná Hora, Czech Republic
Field-hunting tip
Look in oxidized zones of arsenic-rich hydrothermal veins country — that is the host setting where zýkaite typically forms. If you start seeing arsenopyrite, pyrite, symplesite in float, you are in the right ground. Field specimens usually show a botryoidal, crusts, or radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find zýkaite on the map
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