Biphosphammite

Chemical formula: H₂(N₃-H₄)PO₄

Biphosphammite is a rare phosphate mineral, an acidic ammonium phosphate, found mainly in caves with bat guano.

## Characteristics Biphosphammite is a very rare mineral from the phosphate group. It forms colorless or white, fine crystals and efflorescences, often with a vitreous luster. It usually occurs as granular or powdery aggregates, and well-formed crystals are extremely rare. It is a secondary mineral, forming under specific conditions. ## Physical Properties Due to its extreme rarity and small crystal size, many of biphosphammite's physical properties have not been fully studied. It is a very soft and brittle mineral. Its Mohs hardness is low, estimated at around 1. It has a low density, comparable to other hydrated phosphates. ## Colors and Varieties This mineral is typically colorless to white. No color varieties or commercial varieties are distinguished. ## History and Name Biphosphammite was first described in 1870 by the American chemist and mineralogist Charles Upham Shepard. The name refers to its chemical composition – it is a phosphate (phosphammite) with a doubled (bi-) content of ammonium and hydrogen cations compared to phosphammite. ## Uses Biphosphammite has no industrial application. It is of purely scientific and collector's interest as a very rare mineral.

Properties

Mohs hardness: 1
Luster: Vitreous
Streak: White
Density: 2.04
Cleavage: Perfect on {010}
Fracture: Uneven
Transparency: Transparent
Crystal system: Tetragonal

Diagnostic features

## Identification Identifying biphosphammite in the field is practically impossible without specialized analysis. A key feature is its occurrence in guano caves. In the laboratory, it is identified based on its characteristic reaction – solubility in water – and using analytical methods such as X-ray diffraction (XRD). ## Distinguishing from Similar Minerals It can be confused with other secondary phosphates found in guano, such as phosphammite, struvite, or newberyite. Differentiation requires chemical or crystallographic analysis. Biphosphammite is distinguished by its solubility in water, which is not typical for most minerals. ## Crystal Forms It forms very small, tabular or prismatic crystals, usually grouped into granular, powdery, or crusty aggregates. Single, well-formed crystals are rarely observed.

Geological environment

## Genesis Biphosphammite is a mineral of organic (organogenic) origin. It forms as a product of the reaction of phosphoric acid, derived from the decomposition of bat or seabird guano, with ammonia released in the same process. It crystallizes in a dry, ammonia-rich environment. ## Mineral Associations It most often co-occurs with other phosphate minerals formed in guano, such as phosphammite, struvite, salammoniac, as well as gypsum and calcite. ## Localities It is an extremely rare mineral. It was found on the Guañape Islands off the coast of Peru (type locality). Its occurrence has also been confirmed in Pedro Caves, on Mona Island in Puerto Rico, and in several other caves worldwide where guano deposits are found.

Rarity

Very rare

For collectors

## Quality Criteria Due to its immense rarity, any analytically confirmed biphosphammite specimen is valuable to specialized collectors. Samples with visible, even microscopic, crystals are most highly prized. It is most often found as efflorescences or powdery aggregates on the host rock or on other minerals from the guano paragenesis. ## Popular Localities The most "classic" specimens, although practically unavailable on the market, come from the Guañape Islands in Peru. A few microminerals come from caves on Mona Island in Puerto Rico.

Care and storage

## Cleaning Biphosphammite specimens are extremely sensitive to water, in which they dissolve. Wet cleaning is absolutely forbidden. Only very careful dust removal with a soft brush or a stream of compressed air from a distance is permissible. ## What to Avoid Avoid contact with water, water vapor, and all liquids. The mineral is hygroscopic and absorbs moisture from the air, leading to its decomposition. It must be protected from high humidity, temperature changes, and all chemicals. ## Storage Biphosphammite specimens must be stored in hermetic, tightly sealed containers (e.g., "perky box" type) with a desiccant (e.g., silica gel). Exposure to open air is impossible and leads to rapid degradation of the mineral.

Sources

IMA Mineral List (CNMNC)