Sigismundite is a rare arsenate mineral found primarily in tin-rich hydrothermal veins. Collectors look for its distinctive brownish, platy crystal clusters occurring alongside other secondary minerals in oxidized zones.
Is this sigismundite?
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 sigismundite with a known reference. Sigismundite sits at Mohs 4 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Sigismundite leaves a yellowish-brown streak.
- 3Read the lusterHold the specimen under a strong light. Sigismundite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow-brown, brown, dark brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, crusts, aggregates.
Often confused with
Sigismundite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Sigismundite leaves yellowish-brown, Duftite leaves light green.
How to tell apart: Streak differs — Sigismundite leaves yellowish-brown, Conichalcite leaves light green.
How to tell apart: Streak differs — Sigismundite leaves yellowish-brown, Tsumcorite leaves yellowish.
Often found alongside sigismundite
Minerals reported to co-occur with sigismundite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ca,Pb)(Zn,Fe³⁺,Mn²⁺)₂(AsO₄)₂(OH,H₂O)₂
- Mohs hardness
- 4
- Density
- 4.26 g/cm³
- Streak
- Yellowish-brown
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Platy Crystals, Crusts, Aggregates
- Cleavage
- Good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins in Tin Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find sigismundite
Classic worldwide localities
- Siglo Veinte mine, Llallagua, Bolivia
Field-hunting tip
Look in hydrothermal veins in tin deposits country — that is the host setting where sigismundite typically forms. If you start seeing wurtzite, pyrite, cassiterite in float, you are in the right ground. Field specimens usually show a platy crystals, crusts, aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find sigismundite on the map
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