Metacinnabar is a rare cubic polymorph of mercury sulfide that is easily distinguished from its trigonal relative, Cinnabar, by its dark, metallic color and black streak. It often forms as an alteration product of other mercury ores and is frequently found in low-temperature hydrothermal veins. Collectors should handle it with care due to its significant mercury content.
Is this metacinnabar?
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 metacinnabar with a known reference. Metacinnabar sits at Mohs 3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: black, gray black.
- 5Look at form & habitCrystal system: cubic. Typical habit: encrustations, granular.
Often confused with
Metacinnabar vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Metacinnabar leaves black, Cinnabar leaves scarlet; luster reads metallic on Metacinnabar and adamantine, inclining to metallic when dark; dull in friable material on Cinnabar.
How to tell apart: Streak differs, so Metacinnabar leaves black, Galena leaves lead-gray.
How to tell apart: Streak differs, so Metacinnabar leaves black, Sphalerite leaves pale brown to pale yellow and white; luster reads metallic on Metacinnabar and resinous to adamantine on Sphalerite.
Often found alongside metacinnabar
Minerals reported to co-occur with metacinnabar. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- HgS
- Mohs hardness
- 3
- Density
- 7.65 g/cm³
- Colors
- BlackGray black
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Encrustations, granular
- Cleavage
- None
- Rarity
- Uncommon
- Uses
- Collector, Ore of mercury
- Host rock
- In mercury deposits formed under low-temperature near-surface conditions
Where rockhounds find metacinnabar
Classic worldwide localities
- Redington mine (type locality) and other properties, near Knoxville, Napa Co., California, USA
- Ryne mine, Mt. Diablo, Contra Costa Co., California, USA
- New Almaden, Santa Clara Co., California, USA
- Skaggs Springs, Sonoma Co., California, USA
- Read Island, Nanaimo mining division, British Columbia, Canada
- San Onofre, near Plateros, Zacatecas, Mexico
Field-hunting tip
Where it forms: In mercury deposits formed under low-temperature near-surface conditions. If you start seeing cinnabar, mercury, wurtzite in float, you are in the right ground. Typical habit: encrustations, granular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify metacinnabar?+
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Is metacinnabar safe to handle?+
What rocks look like metacinnabar?+
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Find metacinnabar on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
