Callaghanite is a rare copper-magnesium carbonate mineral typically found as small, vibrant blue to blue-green platy crystals. It is highly sought after by mineral collectors, specifically occurring in altered brucite-magnesite deposits where it forms as a secondary mineral.
Is this callaghanite?
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 callaghanite with a known reference. Callaghanite 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. Callaghanite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Callaghanite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: blue, blue-green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, crusts, radial aggregates.
Often confused with
Callaghanite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Callaghanite leaves white, Malachite leaves light green.
How to tell apart: Streak differs, so Callaghanite leaves white, Azurite leaves light blue; luster reads vitreous on Callaghanite and vitreous to dull on Azurite.
How to tell apart: Callaghanite is noticeably harder (Mohs 3 vs. 2); streak differs, so Callaghanite leaves white, Aurichalcite leaves pale blue; luster reads vitreous on Callaghanite and pearly on Aurichalcite.
Often found alongside callaghanite
Minerals reported to co-occur with callaghanite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₄Mg₄(CO₃)₃(OH)₁₈·2H₂O
- Mohs hardness
- 3
- Density
- 2.47 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Platy Crystals, Crusts, Radial Aggregates
- Cleavage
- Perfect On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Altered Magnesium-rich Rocks, Hydrothermal Alteration Zones
- Typical price
- $50-300 per specimen
Where rockhounds find callaghanite
Classic worldwide localities
- Gabbs, Nevada, USA
- Långban, Sweden
Field-hunting tip
Look in altered magnesium-rich rocks, hydrothermal alteration zones country, the host setting where callaghanite typically forms. If you start seeing magnesite, brucite, hydromagnesite in float, you are in the right ground. Field specimens usually show a platy crystals, crusts, radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify callaghanite?+
Where is callaghanite found?+
How much is callaghanite worth?+
Is callaghanite safe to handle?+
What rocks look like callaghanite?+
What minerals are found with callaghanite?+
What kind of rock does callaghanite form in?+
What is callaghanite used for?+
Find callaghanite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
