Bismoclite is a rare bismuth oxychloride that typically forms in the oxidized zones of ore deposits. It is often identified by its pearly luster on cleavage surfaces and its significantly high density for a non-metallic appearing mineral.
Is this bismoclite?
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 bismoclite with a known reference. Bismoclite sits at Mohs 2-2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: greasy, silky, pearly on cleavage surfaces; dull to earthy when massive.
- 4Match the color rangeCompare against the expected color range: brown, colorless, gray, yellow, yellow brown.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: platy crystals, crusts, massive.
Often confused with
Bismoclite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Bismoclite leaves white, Bismutite leaves gray; luster reads greasy, silky, pearly on cleavage surfaces; dull to earthy when massive on Bismoclite and vitreous, waxy, may be dull to earthy on Bismutite.
How to tell apart: Luster reads greasy, silky, pearly on cleavage surfaces; dull to earthy when massive on Bismoclite and adamantine, pearly on {001} on Matlockite.
Often found alongside bismoclite
Minerals reported to co-occur with bismoclite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- BiOCl
- Mohs hardness
- 2-2.5
- Density
- 7.36 g/cm³
- Streak
- White
- Luster
- Greasy, silky, pearly on cleavage surfaces; dull to earthy when massive
- Transparency
- Opaque, transparent in fine grains
- Crystal system
- Tetragonal
- Crystal habit
- Platy crystals, crusts, massive
- Cleavage
- Perfect on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In an alluvial specimen, found near bismuth-bearing granite pegmatites (Jackals Water, South Africa); in greisen (Bygoo, Australia)
Where rockhounds find bismoclite
Classic worldwide localities
- Eagle and Blue Bell mines, Tintic district, Juab Co., Utah, USA
- Grizzly Bear and other mines, Goldfield, Esmeralda Co., Nevada, USA
- Mt. Holland, Western Australia, and Bygoo, New South Wales, Australia
- Falcacci mine, Rio Marina, Elba, Italy
- Dalbeattie, Kirkcudbrightshire, Scotland
- Croft Gothal mine, Cornwall, England
Field-hunting tip
Where it forms: In an alluvial specimen, found near bismuth-bearing granite pegmatites (Jackals Water, South Africa); in greisen (Bygoo, Australia). If you start seeing bismutite, mica, bismuthinite in float, you are in the right ground. Typical habit: platy crystals, crusts, massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify bismoclite?+
Where is bismoclite found?+
Is bismoclite safe to handle?+
What rocks look like bismoclite?+
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Find bismoclite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
