Ammineite

Chemical formula: Cu<sup>2+</sup>Cl<sub>2</sub>(N<sup>3-</sup>H<sub>3</sub>)<sub>2</sub>

Ammineite is a very rare copper mineral from the halide group, containing ammonia molecules in its structure, found in guano deposits.

## Characteristics Ammineite is a rare, secondary copper mineral distinguished by the presence of ammonia (NH₃) in its crystal structure. It forms small, prismatic or tabular crystals of an intense blue color. They usually occur as radial or divergent aggregates, growing on rock surfaces. Due to its unique chemical composition and genesis, it is a mineral of great scientific importance. ## Physical Properties Ammineite crystals exhibit a vitreous luster and are transparent to translucent. Its density is approximately 2.19 g/cm³. The hardness of the mineral has not been precisely determined due to the small size and fragility of the crystals, which makes standard tests difficult. ## Colors and Varieties Ammineite occurs exclusively in shades of blue, from light blue to sapphire. No color or commercial varieties are known. ## History and Name The mineral's name comes from the ammine group (ammonia, NH₃), a key component of its chemical structure. It was officially recognized as a new mineral species by the International Mineralogical Association (IMA) in 2010. It was discovered in Pabellón de Pica in the Iquique province (Tarapacá region, Chile). ## Applications Due to its extreme rarity and small crystal size, ammineite has no industrial applications. It is solely an object of scientific interest and a prized acquisition for advanced collections of rare minerals and micromineralogical specimens.

Properties

Luster
Vitreous
Streak
Light blue
Density
2.19
Cleavage
Perfect on {010}, good on {100}
Transparency
Transparent to translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification The key diagnostic feature of ammineite is its unique occurrence environment - guano deposits in an extremely dry climate. The intense blue color, vitreous luster, and characteristic radial aggregates of small, prismatic crystals are also important clues. However, final identification requires advanced analytical methods. ## Distinguishing from Similar Minerals Ammineite can be confused with other blue secondary copper minerals, such as chalcanthite, azurite, or linarite. However, chalcanthite is readily soluble in water and forms under different conditions. Azurite reacts violently with hydrochloric acid, which is not observed with ammineite. Linarite usually has a deeper, more intense color. The most important distinguishing criterion, however, is the mineral paragenesis, i.e., co-occurrence with other rare minerals from guano deposits, such as joanneumite and sal ammoniac. ## Crystal Forms Crystals are most often elongated, prismatic, or flattened (tabular). They usually form small, divergent or radial groups and aggregates. Single, well-formed crystals are rarely found.

Geological environment

## Genesis Ammineite is a secondary mineral, formed under very specific conditions. Its genesis is related to the reaction of copper-rich solutions with ammonia-rich fluids. The source of ammonia is decomposing seabird droppings (guano) in a desert environment with extremely low humidity. ## Mineral Associations This mineral occurs in association with other rare species characteristic of guano deposits. It most often co-occurs with joanneumite, sal ammoniac, halite, and darapskite. ## Localities The only confirmed and described occurrence of ammineite in the world is its type locality - Pabellón de Pica, located in the Atacama Desert in the Iquique province in northern Chile.

Rarity

Very rare

For collectors

## Quality Criteria For such a rare mineral, any specimen with visible, well-formed crystals is considered valuable. The most highly prized samples are those with large (for this mineral, i.e., a few millimeters), intensely blue crystals forming aesthetic, radial aggregates on a small rock matrix. An additional advantage is the co-occurrence with other rare minerals from this locality, especially joanneumite. ## Popular Localities All ammineite specimens available on the collector's market come from a single location in the world: Pabellón de Pica in Chile. This is the only known locality for this mineral.

Care and storage

## Cleaning Ammineite specimens are extremely delicate and potentially unstable. Cleaning should be kept to an absolute minimum. Only careful dust removal with a soft brush or a stream of compressed air from a safe distance is permissible. Any contact with water or other liquids should be avoided. ## What to Avoid The mineral is sensitive to moisture and water, which can lead to its dissolution or chemical degradation. It should be protected from high temperatures, direct sunlight (risk of fading), and all chemicals, especially acids and bases. Changes in air humidity can be harmful to it. ## Storage It is recommended to store specimens in a sealed, dry container, e.g., a "micromount" box, away from sources of light and heat. Stable environmental conditions are crucial for maintaining the mineral's integrity.

External references

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