Sigismundite is a rare barium iron calcium phosphate. It was approved as a distinct mineral species in 1994, from material found in Italy.
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. Streak: yellowish-brown.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 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 pale green to white; luster reads vitreous on Sigismundite and dull to vitreous on fractures on Duftite.
How to tell apart: Streak differs, so Sigismundite leaves yellowish-brown, Conichalcite leaves green.
How to tell apart: Streak differs, so Sigismundite leaves yellowish-brown, Tsumcorite leaves yellow.
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
- BaFe²⁺(CaNa₂)Fe²⁺₁₃Al(PO₄)₁₁(PO₃OH)(OH)₂
- Mohs hardness
- 4
- 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
Where rockhounds find sigismundite
Classic worldwide localities
- Siglo Veinte mine, Llallagua, Bolivia
Field-hunting tip
Where it forms: hydrothermal veins in tin deposits. If you start seeing wurtzite, pyrite, cassiterite in float, you are in the right ground. Typical habit: platy crystals, crusts, aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify sigismundite?+
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What rocks look like sigismundite?+
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Find sigismundite on the map
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