Dewindtite

Chemical formula: H₂Pb₂+₃(U₆+O₂)₆O₄(PO₄)₄·₁₂H₂O

Dewindtite is a rare, bright yellow uranium mineral, forming small, tabular crystals and characteristic radial aggregates.

## Characteristics Dewindtite is a hydrated lead uranyl phosphate, belonging to the phosphuranylite group. It occurs as very small, tabular or lath-like crystals, which often form radial aggregates, rosettes, or spherulitic clusters. Its most characteristic feature is its intense, canary-yellow or greenish-yellow color. Specimens usually appear as thin coatings and crusts on host rocks. ## Physical Properties Dewindtite crystals exhibit a vitreous to waxy luster, which can be pearly on cleavage surfaces. It is a relatively soft mineral, with a Mohs hardness of 3-4. It is transparent to translucent. Due to its lead and uranium content, it has a high density, approximately 5.03 g/cm³. ## Colors and Varieties This mineral is monochromatic, displaying shades from canary-yellow, through golden-yellow, to greenish-yellow. No color varieties or commercial varieties are distinguished. ## History and Name Dewindtite was first described in 1922 by the Belgian mineralogist Alfred Schoep. He named it in honor of Dr. Jean Dewindt, a Belgian geologist from Ghent University, who tragically died near Lake Tanganyika during fieldwork. ## Uses Due to its rarity and small crystal size, dewindtite has no industrial applications. It is solely an object of interest for collectors specializing in uranium minerals and for scientists.

Properties

Mohs hardness: 3-4
Luster: Vitreous, Waxy, Pearly
Streak: Light yellow
Density: 5.03
Cleavage: Perfect on {100}
Fracture: Uneven
Transparency: Transparent to translucent
Crystal system: Orthorhombic

Diagnostic features

## Identification Key diagnostic features of dewindtite include its intensely yellow color, characteristic radial or spherulitic aggregates of small, tabular crystals, and strong fluorescence under ultraviolet light (both short-wave and long-wave). Its high radioactivity is also an important indicator. ## Distinguishing from Similar Minerals Dewindtite can be confused with other yellow secondary uranium minerals, such as torbernite, autunite, uranophane, or phosphuranylite. Differentiation often requires advanced analytical methods (XRD, EDS). Visually, dewindtite is distinguished by its crystal habit (thin tabular crystals with an orthorhombic outline) and aggregate forms (rosettes, spherulites). Unlike autunite, its fluorescence is usually less intense. ## Crystal Forms Crystals are very small, thin-tabular, with an orthorhombic outline, elongated along one of the axes. They most often form fan-shaped, radial aggregates, rosettes, spherulites, and thin coatings and crusts on rocks.

Geological environment

## Genesis Dewindtite is a secondary uranium mineral, formed in the oxidation (weathering) zones of uraninite deposits and other primary uranium minerals. It crystallizes from aqueous solutions rich in uranium, lead, and phosphates, often in the presence of galena, which is a source of lead. ## Mineral Associations This mineral often co-occurs with other secondary uranium minerals. Its most common associations include: torbernite, autunite, dumontite, parsonsite, pyromorphite, uraninite, kasolite, curite, and galena. ## Localities The most important and type locality for dewindtite is the Shinkolobwe mine in Haut-Katanga Province (Democratic Republic of Congo), from which the best specimens originate. It is also known from several other localities worldwide, including the Ruggles mine in Grafton (New Hampshire, USA), deposits in the Wölsendorf area in Bavaria (Germany), and uranium mines in northern Australia.

Rarity

Rare

For collectors

## Quality Criteria The most valued specimens by collectors are those with well-formed, sharp crystals forming aesthetic, radial rosettes or fans. The intensity and purity of the canary-yellow color significantly increase its value. Contrast with the dark host rock and the presence of associated minerals that create attractive compositions are also important. Due to the small size of the crystals, specimens with larger aggregates visible to the naked eye are particularly sought after. ## Popular Localities By far the most desirable and classic dewindtite specimens come from its type locality – the Shinkolobwe mine in the Democratic Republic of Congo. Specimens from this location are considered exemplary for this species.

Care and storage

## Cleaning Dewindtite specimens are extremely delicate and brittle. Cleaning should be kept to an absolute minimum. If necessary, a very soft brush can be used to remove dust or compressed air from a safe distance. Avoid contact with water, which can damage the mineral. ## What to Avoid Dewindtite is a radioactive and toxic mineral due to its uranium and lead content. Inhalation of dust and direct skin contact must be strictly avoided. It must not be heated or exposed to any chemicals. It is sensitive to changes in temperature and humidity. ## Storage Specimens should be stored in sealed, well-labeled containers, away from other minerals that could be damaged by radiation. It is recommended to keep them in a dry place, away from heat sources and direct sunlight. Due to its radioactivity, it should be stored with appropriate precautions, away from areas of permanent human presence.

Sources

IMA Mineral List (CNMNC)