Melanterite is a secondary sulfate mineral typically formed by the oxidation of iron sulfides like pyrite in damp mine environments. It is characterized by its bright green color and sweet, astringent taste, though it is highly unstable and will crumble into a white powder if exposed to dry air for too long.
Is this melanterite?
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 melanterite with a known reference. Melanterite sits at Mohs 2, 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: vitreous.
- 4Match the color rangeCompare against the expected color range: green, yellow green, brownish black, bluish green, greenish white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: capillary, efflorescences, encrustations.
Often confused with
Melanterite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside melanterite
Minerals reported to co-occur with melanterite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- FeSO₄·7H₂O
- Mohs hardness
- 2
- Density
- 1.895-1.898 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Capillary, efflorescences, encrustations
- Cleavage
- On {001}, perfect; on {120}, distinct
- Rarity
- Common
- Uses
- Collector, Educational
- Host rock
- A post-mine product of oxidation of pyrite and marcasite ores; rarely a volcanic sublimate
Where rockhounds find melanterite
4 mapped spotsClassic worldwide localities
- Alma mine, Leona Heights, Alameda Co., and the Island Mountain mine, Trinity Co., California, USA
- Ducktown, Polk Co., Tennessee, USA
- Butte, Silver Bow Co., Montana, USA
- Lucky Boy mine, Bingham district, Salt Lake Co., Utah, USA
- Rammelsberg mine, near Goslar, Harz Mountains, Germany
- Falun, Sweden
Field-hunting tip
Where it forms: A post-mine product of oxidation of pyrite and marcasite ores; rarely a volcanic sublimate. If you start seeing pisanite, chalcanthite, epsomite in float, you are in the right ground. Typical habit: capillary, efflorescences, encrustations. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Missouri, Arizona. Start trip planning there.
Common questions
How do you identify melanterite?+
Where is melanterite found?+
Can I find melanterite in the United States?+
Is melanterite safe to handle?+
What rocks look like melanterite?+
What minerals are found with melanterite?+
What kind of rock does melanterite form in?+
What is melanterite used for?+
Find melanterite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
