Sasaite

Chemical formula: Al₆(PO₄)₅(OH)₃·₃₆H₂O

Sasaite is a very rare and soft hydrated aluminum phosphate, occurring as white, chalk-like or fibrous aggregates.

## Characteristics Sasaite is a hydrated aluminum phosphate with a complex chemical composition. It forms extremely fine-grained, soft, and brittle aggregates that feel like talc or clay. Typical specimens have the appearance of chalk, felted fibers, or dusty coatings. Due to the microscopic size of its crystals, its features are rarely visible to the naked eye. ## Physical Properties This mineral is exceptionally soft, with a Mohs hardness of just 1. It has a very low density, about 1.75 g/cm³, which makes specimens extremely lightweight. The luster is pearly on the few cleavage surfaces or dull and earthy in the case of massive aggregates. Fine crystals can be translucent, but aggregates are usually opaque. ## Colors and Varieties Sasaite is typically white or colorless. No colored or commercial varieties are distinguished. ## History and Name The mineral was first described in 1978 by J. Martini. Its name comes from the discovery locality – the Sasa lead and zinc mine in North Macedonia, which is its type locality. ## Uses Due to its rarity and small accumulations, sasaite has no industrial application and is solely an object of interest for specialized mineral collectors.

Properties

Mohs hardness: 1
Luster: Pearly to Earthy
Streak: White
Density: 1.75
Cleavage: Perfect on {010}
Transparency: Translucent to Opaque
Crystal system: Orthorhombic

Diagnostic features

## Identification Key diagnostic features include extreme softness (can be scratched with a fingernail), very low density, white color, and occurrence in powdery, chalky, or fibrous masses. Its occurrence environment, often associated with guano, is also characteristic. ## Distinguishing from Similar Minerals It can be confused with other white, secondary phosphate minerals, such as wavellite, crandallite, as well as gypsum or clay minerals (kaolinite). Wavellite often forms radial aggregates, and gypsum, though also soft, has a different crystal habit and perfect cleavage in three directions. Certain identification almost always requires advanced analytical methods, such as X-ray diffraction (XRD). ## Crystal Forms It forms microscopic, bladed or tabular crystals that combine into spherical or fibrous aggregates. Most commonly found as powdery, earthy, or chalk-like coatings and aggregates.

Geological environment

## Genesis This is a secondary mineral, formed under specific conditions. It forms in the oxidation zones of ore deposits or in caves, as a result of the interaction of phosphate-rich solutions (e.g., from the decomposition of bat guano) with aluminosilicate minerals of the surrounding rocks. ## Mineral Associations It co-occurs with other secondary phosphates, such as wavellite and crandallite, as well as with gypsum, gibbsite, and clay minerals. ## Localities The main and best-known localities are the Sasa mine in North Macedonia (type locality) and the General Post Office Cave in Western Australia. It is an extremely rare mineral worldwide.

Rarity

Very rare

For collectors

## Quality Criteria In the case of sasaite, collectible value lies not in the aesthetics of individual crystals, but in the richness and purity of the aggregates. Specimens with well-defined fibrous or spherical aggregates are prized, as is material from the type locality, which is best documented. ## Popular Localities Specimens from the Sasa mine in North Macedonia are most sought after by collectors. Material from the cave in Western Australia is also valued but less commonly available on the market.

Care and storage

## Cleaning Specimens are extremely delicate and partially soluble in water. Cleaning should be limited to very carefully removing dust with a soft, dry brush or a gentle stream of compressed air from a safe distance. ## What to Avoid Absolutely avoid contact with water and other liquids. The mineral is sensitive to heat, which can lead to its dehydration and destruction of its structure. It should be protected from shocks, impacts, and any pressure. ## Storage It is best stored in a closed, stable environment, e.g., in a "micromount" box, to protect it from mechanical damage, dust, and humidity fluctuations.

Sources

IMA Mineral List (CNMNC)