Aurichalcite is a stunning secondary mineral known for its delicate, acicular crystals that often form beautiful, sky-blue tufts and crusts. Collectors treasure it for its vibrant color and intricate, radiating crystal habits, which are commonly found in the oxidized zones of base metal ore deposits.
Is this aurichalcite?
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 aurichalcite with a known reference. Aurichalcite sits at Mohs 1-2, 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: silky to pearly.
- 4Match the color rangeCompare against the expected color range: pale blue, greenish-blue, sea-green, pale green, sky blue.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular, druse, encrustations.
Often confused with
Aurichalcite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Hemimorphite is the harder of the two (Mohs 4.5-5 vs. 1-2); streak differs, so Aurichalcite leaves light blue, Hemimorphite leaves white; luster reads silky to pearly on Aurichalcite and vitreous, subpearly, adamantine, rarely silky on Hemimorphite.
How to tell apart: Malachite is the harder of the two (Mohs 3.5-4 vs. 1-2); streak differs, so Aurichalcite leaves light blue, Malachite leaves pale green; luster reads silky to pearly on Aurichalcite and adamantine to vitreous; silky if fibrous; dull to earthy if massive on Malachite.
How to tell apart: Streak differs, so Aurichalcite leaves light blue, Chrysocolla leaves white when pure; luster reads silky to pearly on Aurichalcite and vitreous, porcelaneous, earthy on Chrysocolla.
Often found alongside aurichalcite
Minerals reported to co-occur with aurichalcite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Zn,Cu)₅(CO₃)₂(OH)₆
- Mohs hardness
- 1-2
- Density
- 3.96 g/cm³
- Colors
- Streak
- Light blue
- Luster
- Silky to pearly
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular, druse, encrustations
- Cleavage
- On {010} and {100}, perfect
- Rarity
- Common
- Uses
- Collector
- Host rock
- In the oxidized zones of copper and zinc deposits
Where rockhounds find aurichalcite
Classic worldwide localities
- Bisbee, Cochise Co., in the Silver Hill mine, Pima Co., and at the 79 mine, Gila Co., Arizona, USA
- Cerro Gordo, Inyo Co., California, USA
- Kelly and Graphic mines, Magdalena, Socorro Co., New Mexico, USA
- Tintic district, Juab Co., at the Hidden Treasure mine, Tooele Co., in the Apex mine, near St. George, Washington Co., and from Big Cottonwood Canyon, Salt Lake Co., Utah, USA
- Loktevskii mine, upper Loktevka River, west Altai Mountains, Russia
- Monteponi, and in the Rosas mine, Sulcis, Sardinia, Italy
Field-hunting tip
Where it forms: In the oxidized zones of copper and zinc deposits. If you start seeing rosasite, smithsonite, hemimorphite in float, you are in the right ground. Typical habit: acicular, druse, encrustations. Train your eye for that shape before scanning the outcrop.
Common questions
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Find aurichalcite on the map
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