Phuralumite

Chemical formula: Al<sub>2</sub>[(U<sup>6+</sup>O<sub>2</sub>)<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub>O(OH)](OH)<sub>3</sub>(H<sub>2</sub>O)<sub>9</sub>

A rare secondary mineral from the uranyl phosphate group, forming characteristic yellow, acicular crystals.

## Characteristics Furalumite is a hydrated aluminum uranyl phosphate, occurring in the oxidation zones of uranium deposits. It forms small but well-developed acicular or bladed crystals, which often arrange into radial aggregates, rosettes, and crusts on the host rock. Its vibrant, canary-yellow or golden-yellow color makes it easily noticeable despite the small size of the crystals. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of about 3. It is brittle and has a density of approximately 3.99 g/cm³. The luster is typically vitreous, sometimes with a waxy or greasy sheen on fracture surfaces. It is transparent to translucent. It exhibits strong, greenish-yellow fluorescence under ultraviolet light (both shortwave and longwave). ## Colors and Varieties Furalumite occurs in uniform shades of yellow – from pale yellow, through canary yellow, to intense golden yellow. No color varieties or commercial varieties are distinguished. ## History and Name The mineral's name refers to its chemical composition: **Ph**osphate, **Ur**anium, and **Alum**inium. It was first described in 1979 by Michel Deliens and Paul Piret based on specimens found in the Kobokobo pegmatite in the Democratic Republic of Congo. ## Uses Due to its rarity and occurrence in small quantities, furalumite has no industrial applications. However, it is a valued and sought-after collector's mineral. As a uranium mineral, it is radioactive and is an object of scientific research.

Properties

Mohs hardness
3
Luster
Vitreous to Waxy
Streak
Light yellow
Density
3.99
Cleavage
Perfect on {100}
Fracture
Uneven
Transparency
Transparent to Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification The most important diagnostic features of furalumite are its intense yellow color, acicular crystal habit forming radial aggregates, and strong greenish-yellow fluorescence under UV light. Its occurrence in paragenesis with other secondary uranium minerals is also a key indicator. ## Distinguishing from Similar Minerals Furalumite can be confused with other yellow, acicular uranyl minerals, such as uranophane or some forms of metaautunite. Uranophane often forms fibrous aggregates rather than radial aggregates of sharp needles. Definitive differentiation often requires chemical analysis (EDS) or X-ray diffraction (XRD). ## Crystal Forms Crystals are small, acicular or elongated, bladed. They most often occur in the form of radial aggregates resembling hedgehogs or stars, as well as dense crusts and coatings.

Geological environment

## Genesis Furalumite is a secondary mineral, formed in the oxidation (weathering) zone of granitic pegmatites rich in uraninite. It forms as a result of the action of phosphate-rich waters on primary uranium minerals in the presence of aluminum, derived from the decomposition of feldspars or micas. ## Mineral Associations This mineral often co-occurs with other secondary uranyl phosphates, such as upalite, threadgoldite, parsonsite, torbernite, as well as with quartz, mica, and clay minerals. ## Localities The most important and historical locality for furalumite, from which the best collector specimens originate, is the Kobokobo pegmatite in Kivu Province, Democratic Republic of Congo. This is its type locality.

Rarity

Very rare

For collectors

## Quality Criteria The most highly valued furalumite specimens are characterized by an abundance of well-formed, sharp crystals forming aesthetic, radial aggregates. The intensity and purity of the yellow color are crucial. The attractiveness is also enhanced by a contrasting rock matrix and the presence of other rare associated minerals. ## Popular Localities Practically all valuable collector specimens of furalumite come from a single location in the world – the Kobokobo pegmatite in the Democratic Republic of Congo.

Care and storage

## Cleaning Furalumite specimens should only be dry-cleaned, using a soft brush or compressed air to remove dust. Avoid contact with water, which can lead to rehydration and damage to the delicate crystals. ## What to Avoid As a uranium mineral, furalumite is radioactive. Direct contact should be limited, and hands should be washed after each interaction. It should not be stored in areas of permanent human habitation. The mineral is sensitive to high temperatures, which can cause water loss from its structure. Avoid all chemicals and ultrasonic cleaners. ## Storage It is recommended to store specimens in closed, labeled containers (e.g., micromount type), away from bedrooms and living rooms. For richer samples, specialized containers with anti-radiation shielding may be considered. It should be protected from dust and mechanical damage.

Sources

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