Dondoellite

Chemical formula: Ca<sub>2</sub>Fe<sup>2+</sup>(PO<sub>4</sub>)<sub>2</sub>·2H<sub>2</sub>O

Dondoellite is a very rare hydrated calcium iron phosphate, forming microscopic, bladed brown crystals.

## Characteristics Dondoellite is a mineral from the phosphate group, chemically classified as a hydrated calcium iron phosphate. It occurs as very small, bladed or tabular crystals, rarely exceeding 0.2 mm in length. These crystals often form radial or spherulitic aggregates. Due to the microscopic size of the crystals, its visual features are difficult to observe without magnification. ## Physical Properties Dondoellite crystals exhibit a vitreous luster. They are brittle, and their hardness and density have not been precisely measured due to the small size of the samples. The mineral is transparent to translucent. ## Colors and Varieties Dondoellite has a characteristic brown to reddish-brown color. No varieties have been described. ## History and Name The mineral was discovered in a granitic pegmatite near the town of Dondo in Mozambique, from which it derives its name. It was officially approved by the International Mineralogical Association (IMA) in 2018. It was described by a team of mineralogists, including Oleg I. Siidra and Igor V. Pekov. ## Uses Due to its extreme rarity and microscopic size, dondoellite has no industrial applications. It is solely an object of scientific interest and a collector's item for specialized collectors of rare minerals.

Properties

Luster
Vitreous
Streak
Light brown
Cleavage
Perfect on {100}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Triclinic

Diagnostic features

## Identification Identification of dondoellite is possible almost exclusively by advanced analytical methods, such as Raman spectroscopy and chemical analysis using an electron microprobe (EDS/WDS). Visually, under high magnification, characteristic brown, bladed crystals forming radial aggregates can be observed. ## Distinguishing from Similar Minerals Dondoellite can be confused with other rare phosphates found in similar environments, such as anapaite or fairfieldite. Differentiation requires specialized chemical and crystallographic analysis. Unlike the often greenish anapaite, dondoellite has a brown color. ## Crystal Forms The mineral forms elongated, bladed or thin-tabular crystals, elongated along the [010] axis. These crystals combine into radial, stellate, or spherulitic (spherical) aggregates up to 0.5 mm in diameter.

Geological environment

## Genesis Dondoellite is a secondary mineral, forming in the late stages of crystallization of granitic pegmatites. It forms in rock cavities and fissures as a result of hydrothermal processes that lead to the alteration of earlier phosphate minerals. ## Mineral Associations This mineral occurs in association with other phosphates and pegmatitic minerals. At the type locality (Dondo, Mozambique), it co-occurs with quartz, microcline, muscovite, beryl, lithiophilite, strengite, cyrilite, jahnsite-(CaMnFe), rockbridgeite, and wardite. ## Localities The only confirmed occurrence of dondoellite in the world is its type locality – a granitic pegmatite in Alto Ligonha, near Dondo, in Zambézia Province, Mozambique.

Rarity

Extremely rare

For collectors

## Quality Criteria As a "micromount" mineral, the collector's value of dondoellite depends on the quality and richness of the crystal aggregates on the rock matrix. The most prized specimens are those with well-formed, radial aggregates of intense, brown color, clearly contrasting with the substrate. The presence of associated minerals that confirm the paragenesis is also important. ## Popular Localities The only source of dondoellite specimens is its type locality in Mozambique. Material from this location is extremely limited, making it one of the rarest minerals available on the collector's market.

Care and storage

## Cleaning Dondoellite specimens are extremely delicate and small. Mechanical or chemical cleaning is not recommended. Any attempts at cleaning may destroy the microscopic crystals. It is best to leave the specimen in its untouched state. ## What to Avoid Avoid contact with all chemicals, ultrasound, and sudden temperature changes. The crystals are brittle and susceptible to mechanical damage. Do not expose it to water, which may affect its hydration structure. ## Storage Specimens should be stored under stable conditions, in sealed "micromount" boxes, to protect them from dust, shocks, and physical damage. Store away from sources of moisture and direct sunlight.

Sources

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