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, so Sigismundite leaves yellowish-brown, Duftite leaves light green.
How to tell apart: Streak differs, so Sigismundite leaves yellowish-brown, Conichalcite leaves light green.
How to tell apart: Streak differs, so 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, 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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