Swaknoite

Chemical formula: (N<sup>3-</sup>H<sub>4</sub>)<sub>2</sub>Ca(PO<sub>3</sub>OH)<sub>2</sub>·H<sub>2</sub>O

Swaknoite is an extremely rare hydrated ammonium calcium phosphate, forming microscopic crystals in bat guano deposits.

## Characteristics Swaknoite is a secondary mineral, occurring as white or colorless, microscopic crystals. It forms aggregates in the form of efflorescences, coatings, and delicate, spherulitic aggregates. Individual crystals are lath-like or elongated tabular, rarely exceeding 0.5 mm in length. Due to their size and fragility, specimens are usually observed under a microscope. ## Physical Properties It is a very soft and brittle mineral. It is characterized by a low density of approximately 1.89 g/cm³. Individual crystals, when sufficiently pure, can be transparent to translucent, with a vitreous luster transitioning to pearly on cleavage surfaces. In mass, aggregates appear opaque and dull. ## Colors and Varieties Swaknoite is a uniformly colored mineral – it occurs as colorless or white. No colored or commercial varieties are known. ## History and Name The mineral was first identified in Arnhem Cave in Namibia and officially recognized by the IMA in 1990. Its name comes from the acronym SWAKNO, which stands for the speleological working group operating within the South West African Scientific Society. The name honors the organization's contribution to the study of the region's caves where the discovery was made.

Properties

Luster
Vitreous to Pearly
Streak
White
Density
1.89
Cleavage
Perfect on {010}
Transparency
Transparent to Translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification A diagnostic feature is its specific occurrence environment – caves with bat guano deposits. White color, the form of small, lath-like crystals in spherulitic aggregates, and co-occurrence with other rare guano phosphates are key indicators. Final identification requires advanced analytical methods, such as X-ray diffraction (XRD). ## Distinguishing from Similar Minerals Swaknoite can be confused with other white minerals formed in caves, such as gypsum, calcite, and especially other guano phosphates (e.g., biphosphammite, archerite). Distinguishing it with the "naked eye" is practically impossible. The crystal habit visible under a microscope can be an indicator, but only chemical analysis provides certainty. ## Crystal Forms Crystals are very small, lath-like or thin-tabular, elongated along one axis. They usually form radial or spherulitic aggregates, as well as thin efflorescences and coatings on the host rock or on older guano layers.

Geological environment

## Genesis Swaknoite is a mineral of organic origin. It forms as a result of chemical reactions between solutions rich in phosphoric acid, derived from the decomposition of bat guano, and calcium-rich carbonate rocks (limestones, dolomites) forming the cave walls. ## Mineral Associations This mineral occurs in association with other rare guano minerals. The most common associations include mundrabillite, arcanite, archerite, biphosphammite, and gypsum. ## Localities It is an extremely rare mineral, known from only a few localities worldwide. The type locality and the main source of the best specimens is Arnhem Cave, located in the Khomas region of Namibia.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of swaknoite specimens is primarily judged by the richness and aesthetics of the microcrystalline aggregates. The most valued samples are those with well-formed, microscopically visible spherulites or crystal rosettes, densely covering a small fragment of the host rock. The presence of other well-crystallized associated minerals is an additional advantage. ## Popular Localities The only known and significant locality from a collector's point of view is the type locality – Arnhem Cave in Namibia. Specimens from this location are the reference point for the species.

Care and storage

## Cleaning Swaknoite specimens are extremely delicate and sensitive to water. Cleaning should be limited to very careful dust removal using a soft, dry brush or a photographic blower. Absolutely avoid contact with water and other liquids, which can dissolve or damage the mineral. ## What to Avoid Avoid water, chemical solutions, ultrasound, high humidity, sudden temperature changes, and shocks and impacts. It is one of the most sensitive collector's minerals. ## Storage It is recommended to store specimens only in tightly sealed containers, preferably in specialized "micromount" boxes, which protect against mechanical damage and humidity changes. Store in a dry, thermally stable place, away from direct sunlight.

Sources

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