Deanesmithite is a rare mercury-chromium sulfide-chromate mineral found primarily in the mercury mines of California. It is highly prized by collectors for its brilliant red color and its association with other rare mercury minerals in hydrothermal vein systems.
Is this deanesmithite?
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 deanesmithite with a known reference. Deanesmithite sits at Mohs <5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: less intense red-orange.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine.
- 4Match the color rangeCompare against the expected color range: orange red.
- 5Look at form & habitCrystal system: triclinic. Typical habit: aggregates, fan shaped, radial.
Often confused with
Deanesmithite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Deanesmithite is noticeably harder (Mohs <5 vs. 2-2.5); streak differs, so Deanesmithite leaves less intense red-orange, Cinnabar leaves scarlet.
How to tell apart: Deanesmithite is noticeably harder (Mohs <5 vs. 2.5); streak differs, so Deanesmithite leaves less intense red-orange, Montroydite leaves yellow-brown; luster reads adamantine on Deanesmithite and vitreous to adamantine on Montroydite.
Often found alongside deanesmithite
Minerals reported to co-occur with deanesmithite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Hg⁺₁₂Hg²⁺₃(CrO₄)S₅
- Mohs hardness
- <5
- Density
- 8.06 g/cm³
- Colors
- Streak
- Less intense red-orange
- Luster
- Adamantine
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Aggregates, fan shaped, radial
- Cleavage
- Good on {110}; fair on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Very rare in a mercury deposit in silicate–carbonate rock hydrothermally altered from serpentinite
Where rockhounds find deanesmithite
Classic worldwide localities
- Clear Creek claim, near the Clear Creek mercury mine, New Idria district, San Benito Co., California, USA
Field-hunting tip
Where it forms: Very rare in a mercury deposit in silicate–carbonate rock hydrothermally altered from serpentinite. If you start seeing cinnabar, edoylerite in float, you are in the right ground. Typical habit: aggregates, fan shaped, radial. Train your eye for that shape before scanning the outcrop.
Common questions
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What rocks look like deanesmithite?+
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Find deanesmithite on the map
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