Althupite

Chemical formula: AlTh<sup>4+</sup>(U<sup>6+</sup>O<sub>2</sub>)<sub>7</sub>(PO<sub>4</sub>)<sub>4</sub>O<sub>2</sub>(OH)<sub>5</sub>·15H<sub>2</sub>O

Althupite is a very rare, radioactive secondary phosphate mineral, forming small, platy crystals of an intense yellow color.

## Characteristics Althupite is a hydrated aluminum, thorium, and uranyl phosphate. It belongs to the group of secondary minerals, formed as a result of the alteration of primary uranium and thorium minerals. It forms very small, thin, platy crystals, rarely exceeding 1 mm in length. These crystals often arrange themselves into fan-shaped or rosette-like aggregates with an intense yellow color, making them attractive micromineralogical specimens. ## Physical Properties This mineral is relatively soft, with a hardness of about 3.5 on the Mohs scale. It is brittle and has a vitreous luster, transitioning to waxy on some surfaces. It is translucent. Due to its uranium and thorium content, it exhibits strong radioactivity. ## Colors and Varieties Althupite occurs in a characteristic bright yellow to yellowish-orange color. No color or commercial varieties are distinguished. ## History and Name The mineral's name, approved in 1987, is derived from the symbols of its constituent elements: **Al** (aluminum), **Th** (thorium), **U** (uranium), and **P** (phosphorus). It was first described by Paul Piret and Michel Deliens based on material from the Kobokobo pegmatite in South Kivu Province, Democratic Republic of Congo. ## Uses Althupite has no industrial applications. It is solely an object of scientific interest and a prized acquisition for advanced mineral collections, especially micromineral collections.

Properties

Mohs hardness
3.5
Luster
Vitreous to Waxy
Streak
Light yellow
Density
3.9-4.0
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Translucent
Crystal system
Triclinic

Diagnostic features

## Identification The most important diagnostic feature of althupite is its strong radioactivity, easily detectable with a Geiger counter. Visually, it is recognized by its characteristic yellow color, thin-platy crystal habit, and tendency to form rosette-like aggregates. Knowledge of associated minerals and locality is also crucial. ## Distinguishing from Similar Minerals Althupite can be easily confused with many other yellow secondary uranyl minerals, such as phuralumite, upalite, meta-autunite, or sabugalite. Many of them occur in the same localities and have a similar appearance. Definitive differentiation is almost exclusively possible using advanced analytical methods, such as X-ray diffraction (XRD) and chemical composition analysis (EDS). ## Crystal Forms Crystals are very thin, platy, with a rectangular or hexagonal outline. They most often occur as fan-shaped, radial, or rosette-like aggregates, growing on host rocks.

Geological environment

## Genesis Althupite is a secondary mineral that crystallizes in the oxidation zones of complex granitic pegmatites. It forms as a result of the weathering and alteration of primary uranium minerals (mainly uraninite) and thorium, in a phosphorus-rich environment. ## Mineral Associations This mineral often co-occurs with other rare, secondary uranyl phosphates. Its most common associations include phuralumite, upalite, vanmeersscheite, mundite, meta-autunite, as well as quartz and feldspars from the primary rock. ## Localities The most important and classic locality for althupite, from which the best specimens originate, is the Kobokobo pegmatite in South Kivu Province, Democratic Republic of Congo. This is its type locality. It is also known from several other pegmatites in the same region.

Rarity

Very rare

For collectors

## Quality Criteria As a micromount mineral, althupite is primarily evaluated based on the quality and form of its crystals. Specimens with sharp, well-formed crystals creating aesthetic, rosette-like or fan-shaped aggregates are most highly valued. An intense, clear color and contrast with the rock matrix are important. Rich associations with other rare secondary minerals are also highly regarded. ## Popular Localities The only locality from which althupite specimens of collector significance originate is the Kobokobo pegmatite in the Democratic Republic of Congo. Specimens from this location set the standard for this species.

Care and storage

## Cleaning Althupite specimens are extremely delicate and brittle. Cleaning should be kept to an absolute minimum. The safest method is to gently remove dust with a soft brush or blow it off with a stream of compressed air from a safe distance. Avoid contact with water and any chemical agents. ## What to Avoid As a highly radioactive mineral, althupite requires special precautions. Direct, prolonged skin contact should be avoided, and inhalation of dust that might arise from specimen damage must be absolutely avoided. It should not be stored near radiation-sensitive materials (e.g., photographic film, some gemstones). It is susceptible to mechanical damage. ## Storage Althupite must be stored in a tightly sealed, durable container (e.g., a plastic "perky box") to prevent the spread of any micro-particles. The container should be clearly labeled with the international radioactivity symbol, the full mineral name, and its location. Specimens should be kept out of reach of children and pets, away from living areas and bedrooms.

External references

Sources

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