Ammineite is an incredibly rare mineral that forms in specific guano-rich environments, most notably in the Atacama Desert. It is chemically unique due to the presence of ammonia in its structure, often found as delicate blue tabular crystals or thin crusts associated with other copper chlorides.
Is this ammineite?
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 ammineite with a known reference. Ammineite sits at Mohs ~1, 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.
- 4Match the color rangeCompare against the expected color range: deep, sky-blue.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: tabular crystals, crusts, or aggregates.
Often confused with
Ammineite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Atacamite is the harder of the two (Mohs 3-3.5 vs. ~1); streak differs, so Ammineite leaves light blue, Atacamite leaves apple-green; luster reads vitreous on Ammineite and adamantine to vitreous on Atacamite.
How to tell apart: Connellite is the harder of the two (Mohs 3 vs. ~1); streak differs, so Ammineite leaves light blue, Connellite leaves pale greenish blue.
How to tell apart: Turquoise is the harder of the two (Mohs 5-6 vs. ~1); streak differs, so Ammineite leaves light blue, Turquoise leaves white to pale greenish blue.
Often found alongside ammineite
Minerals reported to co-occur with ammineite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu(NH₃)₂Cl₂
- Mohs hardness
- ~1
- Density
- 2.31 g/cm³
- Colors
- DeepSky-blue
- Streak
- Light blue
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Tabular crystals, crusts, or aggregates
- Cleavage
- Perfect on {001}, good on {110}
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- Likely the product of the interaction between NH3 from guano and Cu from chalcopyrite in underlying igneous rocks
Where rockhounds find ammineite
Classic worldwide localities
- Calleta Pabellon de Pica, Tarapaca region, Chile
Field-hunting tip
Where it forms: Likely the product of the interaction between NH3 from guano and Cu from chalcopyrite in underlying igneous rocks. If you start seeing halite, atacamite, salammoniac in float, you are in the right ground. Typical habit: tabular crystals, crusts, or aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ammineite?+
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Is ammineite safe to handle?+
What rocks look like ammineite?+
What minerals are found with ammineite?+
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Find ammineite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
