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 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Ammineite leaves a pale blue streak.
- 3Read the lusterHold the specimen under a strong light. Ammineite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: blue, blue-green.
- 5Look at form & habitCrystal system: hexagonal. 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. 2); streak differs — Ammineite leaves pale 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. 2).
How to tell apart: Turquoise is the harder of the two (Mohs 5-6 vs. 2); streak differs — Ammineite leaves pale blue, Turquoise leaves white; luster reads vitreous on Ammineite and waxy on Turquoise.
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
- 2
- Density
- 2.16 g/cm³
- Colors
- Streak
- Pale Blue
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Hexagonal
- Crystal habit
- Tabular Crystals, Crusts, Or Aggregates
- Cleavage
- Perfect Basal
- Rarity
- Rare
- Uses
- Collector, Scientific Research
- Host rock
- Fumarolic Deposits or Nitrate-rich Desert Soils
- Typical price
- $50-500 depending on specimen size and quality
Where rockhounds find ammineite
Classic worldwide localities
- Cerro Pintados, Chile
- Atacama Region, Chile
Field-hunting tip
Look in fumarolic deposits or nitrate-rich desert soils country — that is the host setting where ammineite typically forms. If you start seeing sal-ammoniac, atacamite in float, you are in the right ground. Field specimens usually show a tabular crystals, crusts, or aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find ammineite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
