Cannonite is a rare bismuth sulfate mineral that typically occurs as small, transparent tabular crystals in oxidized mineral deposits. It is most famous from the Tintic district in Utah where it forms as a secondary mineral in mine dumps. Collectors prize it for its rarity and its distinct association with other secondary bismuth minerals.
Is this cannonite?
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 cannonite with a known reference. Cannonite 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: white.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine.
- 4Match the color rangeCompare against the expected color range: colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals.
Often confused with
Cannonite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Cannonite is noticeably harder (Mohs 4 vs. 2.5-3).
How to tell apart: Streak differs, so Cannonite leaves white, Bismutite leaves gray; luster reads adamantine on Cannonite and vitreous, waxy, may be dull to earthy on Bismutite.
Often found alongside cannonite
Minerals reported to co-occur with cannonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Bi₂O(OH)₂SO₄
- Mohs hardness
- 4
- Density
- 6.5 g/cm³
- Colors
- Streak
- White
- Luster
- Adamantine
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular crystals
- Cleavage
- Presumed on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- An alteration product in Cu-Bi-Au-sulfide deposits
Where rockhounds find cannonite
Classic worldwide localities
- Tunnel Extension mine, Marysvale, Ohio district, Piute Co., Utah, USA
- Alfenza, Crodo, Italy
Field-hunting tip
Where it forms: An alteration product in Cu-Bi-Au-sulfide deposits. If you start seeing covellite, cuprobismutite, bismuthinite in float, you are in the right ground. Typical habit: tabular crystals. Train your eye for that shape before scanning the outcrop.
Common questions
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Find cannonite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
