Melanarsite is a rare copper-iron arsenate mineral found primarily in the fumarolic environments of volcanic regions. It typically appears as small, dark, tabular crystals associated with other secondary arsenic minerals. Collectors prize it for its extreme rarity and specific occurrence within volcanic vent systems.
Is this melanarsite?
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 melanarsite with a known reference. Melanarsite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Melanarsite leaves a yellowish brown streak.
- 3Read the lusterHold the specimen under a strong light. Melanarsite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: deep red, dark brown, black.
- 5Look at form & habitCrystal system: triclinic. Typical habit: tabular crystals.
Often confused with
Melanarsite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Melanarsite leaves yellowish brown, Clinoclase leaves bluish-green.
How to tell apart: Streak differs — Melanarsite leaves yellowish brown, Olivenite leaves olive-green; luster reads vitreous on Melanarsite and adamantine on Olivenite.
Often found alongside melanarsite
Minerals reported to co-occur with melanarsite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₅Fe₃(AsO₄)₃(OH)₆·6H₂O
- Mohs hardness
- 3.5
- Density
- 4.2 g/cm³
- Colors
- Streak
- Yellowish Brown
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Tabular Crystals
- Cleavage
- Good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Fumarole Deposits
- Typical price
- $100-500 thumbnail
Where rockhounds find melanarsite
Classic worldwide localities
- Kamchatka Peninsula (Russia)
Field-hunting tip
Look in fumarole deposits country — that is the host setting where melanarsite typically forms. If you start seeing arsenohauchecornite, tenorite, hematite in float, you are in the right ground. Field specimens usually show a tabular crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find melanarsite on the map
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