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. Metacinnabar leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Metacinnabar typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: black, gray, brownish-black.
- 5Look at form & habitCrystal system: cubic. Typical habit: tetrahedral crystals, granular, massive.
Often confused with
Metacinnabar vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Metacinnabar leaves black, Cinnabar leaves scarlet; luster reads metallic on Metacinnabar and adamantine on Cinnabar.
How to tell apart: Streak differs — Metacinnabar leaves black, Galena leaves lead-gray.
How to tell apart: Streak differs — Metacinnabar leaves black, Sphalerite leaves white to yellow-brown; luster reads metallic on Metacinnabar and resinous to submetallic 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
- 7.6-7.7 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Tetrahedral Crystals, Granular, Massive
- Cleavage
- Poor On {110}
- Rarity
- Uncommon
- Uses
- Collector, Ore of Mercury
- Host rock
- Epithermal Mercury Deposits, Hydrothermal Veins
- Typical price
- $20-150 for thumbnail to cabinet specimens
Where rockhounds find metacinnabar
Classic worldwide localities
- Almaden, Spain
- Idrija, Slovenia
- California, USA
- Terlingua, Texas, USA
Field-hunting tip
Look in epithermal mercury deposits, hydrothermal veins country — that is the host setting where metacinnabar typically forms. If you start seeing cinnabar, calcite, quartz in float, you are in the right ground. Field specimens usually show a tetrahedral crystals, granular, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find metacinnabar on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
