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, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale yellowish.
- 3Read the lusterHold the specimen under a strong light. Luster: dull.
- 4Match the color rangeCompare against the expected color range: greenish white, gray white.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: nodular.
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); streak differs, so Zýkaite leaves pale yellowish, Scorodite leaves greenish white; luster reads dull on Zýkaite and vitreous to subadamantine, subresinous on Scorodite.
How to tell apart: Streak differs, so Zýkaite leaves pale yellowish, Pitticite leaves yellow to white; luster reads dull on Zýkaite and waxy, vitreous, greasy, may be dull, earthy 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
- Density
- 2.50 g/cm³
- Colors
- Streak
- Pale yellowish
- Luster
- Dull
- Transparency
- Semitransparent
- Crystal system
- Orthorhombic
- Crystal habit
- Nodular
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- An alteration product of arsenopyrite and pyrite in ancient mine dumps
Where rockhounds find zýkaite
Classic worldwide localities
- Šafary mine dump, near Kaňk, Kutná Hora district, Czech Republic
Field-hunting tip
Where it forms: An alteration product of arsenopyrite and pyrite in ancient mine dumps. If you start seeing kaňkite, scorodite, pitticite in float, you are in the right ground. Typical habit: nodular. Train your eye for that shape before scanning the outcrop.
Common questions
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Find zýkaite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
