Demicheleite-(Cl) is an extremely rare bismuth sulfohalide discovered in volcanic fumaroles. It typically forms as small, red to black crystal aggregates or crusts within sulfur-rich volcanic environments.
Is this demicheleite-(cl)?
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 demicheleite-(cl) with a known reference. Demicheleite-(Cl) sits at Mohs 1.5-2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brown.
- 3Read the lusterHold the specimen under a strong light. Luster: submetallic.
- 4Match the color rangeCompare against the expected color range: red, black.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: tabular to acicular crystals, often as crusts or efflorescences.
Often confused with
Demicheleite-(Cl) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Demicheleite-(Cl) leaves brown, Sulfur leaves white; luster reads submetallic on Demicheleite-(Cl) and resinous on Sulfur.
How to tell apart: Streak differs, so Demicheleite-(Cl) leaves brown, Bismoclite leaves white; luster reads submetallic on Demicheleite-(Cl) and greasy, silky, pearly on cleavage surfaces; dull to earthy when massive on Bismoclite.
Often found alongside demicheleite-(cl)
Minerals reported to co-occur with demicheleite-(cl). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- BiSCl
- Mohs hardness
- 1.5-2
- Density
- 5.934 g/cm³
- Streak
- Brown
- Luster
- Submetallic
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Tabular to acicular crystals, often as crusts or efflorescences
- Cleavage
- None observed
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A product of fumarolic alteration of pyroclastic breccia
Where rockhounds find demicheleite-(cl)
Classic worldwide localities
- La Fossa crater, Vulcano Island, Aeolian archipelago, Sicily, Italy
Field-hunting tip
Where it forms: A product of fumarolic alteration of pyroclastic breccia. If you start seeing demicheleite-, bismoclite, bismuthinite in float, you are in the right ground. Typical habit: tabular to acicular crystals, often as crusts or efflorescences. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify demicheleite-(cl)?+
Where is demicheleite-(cl) found?+
Is demicheleite-(cl) safe to handle?+
What rocks look like demicheleite-(cl)?+
What minerals are found with demicheleite-(cl)?+
What kind of rock does demicheleite-(cl) form in?+
What is demicheleite-(cl) used for?+
Find demicheleite-(cl) on the map
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