Rosasite is a secondary mineral often found as attractive blue to blue-green botryoidal crusts or fibrous aggregates in oxidized copper-zinc mines. It is visually similar to malachite and aurichalcite, requiring careful testing to distinguish it from other copper carbonates.
Is this rosasite?
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 rosasite with a known reference. Rosasite sits at Mohs 4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: light blue.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to silky.
- 4Match the color rangeCompare against the expected color range: blue green, light blue, sky blue.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: encrustations, mammillary, spherical.
Often confused with
Rosasite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Rosasite leaves light blue, Malachite leaves pale green; luster reads vitreous to silky on Rosasite and adamantine to vitreous; silky if fibrous; dull to earthy if massive on Malachite.
How to tell apart: Rosasite is noticeably harder (Mohs 4.5 vs. 1-2); luster reads vitreous to silky on Rosasite and silky to pearly on Aurichalcite.
How to tell apart: Streak differs, so Rosasite leaves light blue, Chrysocolla leaves white when pure.
Often found alongside rosasite
Minerals reported to co-occur with rosasite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Cu,Zn)₂(CO₃)(OH)₂
- Mohs hardness
- 4.5
- Density
- 4.0-4.2 g/cm³
- Streak
- Light blue
- Luster
- Vitreous to silky
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Encrustations, mammillary, spherical
- Cleavage
- In two directions
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- An uncommon secondary mineral in the oxidized zone of Cu–Zn-bearing deposits, typically formed by zinc-bearing solutions on primary copper minerals; may be of post-mine origin
Where rockhounds find rosasite
Classic worldwide localities
- Kelly mine, Magdalena, Socorro Co., New Mexico, USA
- Silver Bill mine, Gleeson, and at Bisbee, Cochise Co., in the 79 mine, Gila Co., and a number of other places, Arizona, USA
- Mohawk mine, San Bernardino Co., California, USA
- Leadville, Lake Co., Colorado, USA
- Rosas mine, Sulcis, Sardinia, Italy
- A number of places in England, as Caldbeck Fells, Cumbria, and mines in Cornwall
Field-hunting tip
Where it forms: An uncommon secondary mineral in the oxidized zone of Cu–Zn-bearing deposits, typically formed by zinc-bearing solutions on primary copper minerals; may be of post-mine origin. If you start seeing malachite, aurichalcite, smithsonite in float, you are in the right ground. Typical habit: encrustations, mammillary, spherical. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify rosasite?+
Where is rosasite found?+
Is rosasite safe to handle?+
What rocks look like rosasite?+
What minerals are found with rosasite?+
What kind of rock does rosasite form in?+
What is rosasite used for?+
Find rosasite on the map
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