Davidite-(Ce)

Chemical formula: Ce₃+(Y,U₄+)Fe₃+₂(Ti₄+,Fe₃+,Cr₃+,V₅+)₁₈(O,OH,F)₃₈

Dawidite-(Ce) is a rare, complex titanium and iron oxide with cerium, forming black, resinous masses with high radioactivity.

## Characteristics Dawidite-(Ce) is a complex oxide from the crichtonite group, containing cerium as the dominant rare earth element. It typically occurs as amorphous (metamict) masses or as irregular grains embedded in the host rock. Rarely, it forms poorly developed, tabular or thick-tabular crystals. Its appearance is unassuming – most often it is a black, pitchy or resinous substance, often covered with yellow or brown weathering products. ## Physical Properties This mineral is characterized by a hardness in the range of 5-6 on the Mohs scale. It has a strong, vitreous to resinous, and sometimes almost pitchy luster. It is opaque. The density is variable, depending on the chemical composition and degree of metamictization, ranging from 4.2 to 5.0 g/cm³. Due to the presence of uranium and thorium, dawidite-(Ce) is a highly radioactive mineral. ## Colors and Varieties Dawidite-(Ce) is usually black, less commonly brownish-black or dark brown. In thin fragments, it may appear translucent brown. No distinct color varieties or commercial varieties are recognized. Variability in chemical composition leads to the existence of other minerals in the dawidite group, such as dawidite-(La) and dawidite-(Y). ## History and Name The name "dawidite" was given in honor of Tannatt William Edgeworth David (1858-1934), a Welsh-Australian geologist and explorer. The suffix "-(Ce)" was added in accordance with the rules for naming minerals with a dominant rare earth element, in this case, cerium. The mineral was originally described from South Australia. ## Applications Due to its rarity and complex chemical composition, dawidite-(Ce) has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals, rare earth minerals, and radioactive minerals.

Properties

Mohs hardness: 5-6
Luster: Vitreous to resinous
Streak: Black to brownish-black
Density: 4.2-5.0
Cleavage: None
Fracture: Conchoidal to uneven
Transparency: Opaque
Crystal system: Trigonal

Diagnostic features

## Identification A key diagnostic feature of dawidite-(Ce) is its strong radioactivity, which can be easily detected with a Geiger counter. Other features include its black color, resinous or pitchy luster, high density, and occurrence as amorphous masses. It is often accompanied by characteristic yellow weathering products. ## Distinguishing from Similar Minerals Dawidite-(Ce) can be confused with other black, heavy, and radioactive minerals, such as uraninite, thorianite, or some varieties of allanite. Uraninite usually has a more pitchy or dull luster and often forms regular crystals. Allanite tends to be less radioactive and often occurs as elongated, prismatic crystals in pegmatites. Accurate identification requires advanced analytical methods (EDS/WDS). ## Crystal Forms Well-formed crystals are extremely rare. If they occur, they take the form of thick, tabular crystals with a hexagonal or trigonal outline. However, this mineral usually forms irregular, amorphous masses and grains, which are the result of metamictization – the destruction of the crystal structure by its own radiation.

Geological environment

## Genesis Dawidite-(Ce) is a mineral of high-temperature hydrothermal processes. It forms in quartz-carbonate veins and in skarns. It is also found in pegmatites and some types of metamorphosed rocks. ## Mineral Associations It often co-occurs with minerals such as rutile, ilmenite, hematite, magnetite, ankerite, quartz, feldspars, as well as uranium and thorium minerals. In weathering zones, it is accompanied by secondary uranium minerals, e.g., carnotite. ## Localities The most important and classic localities for this mineral are in Australia, especially Radium Hill and Olary in South Australia. It also occurs in Tuftan (Telemark province, Norway), in the Arendal area (Norway), and in several locations in Russia (Urals).

Rarity

Very rare

For collectors

## Quality Criteria The collector's appeal of dawidite-(Ce) does not depend on aesthetics, but on its rarity and scientific value. Specimens with rare, even if poorly formed, crystals are most highly prized. A well-documented locality is also important, especially if it is a type locality (terra typica). The size of the specimen is less important than the presence of crystalline forms. ## Popular Localities Specimens from Radium Hill in South Australia are considered classic and most sought after by specialized collectors. Norwegian localities, such as Tuftan, also provide material of reference significance.

Care and storage

## Cleaning Specimens should only be cleaned mechanically, using a soft, dry brush to remove dust. All contact with water and chemicals, which could react with the mineral or its weathering products, should be avoided. ## What to Avoid As a radioactive mineral, it requires special caution. Prolonged, close contact should be avoided, and inhalation of dust, which may arise during processing or damage to the specimen, must be absolutely avoided. It should not be heated or exposed to chemicals. Store away from radiation-sensitive materials. ## Storage Dawidite-(Ce) must be stored in specialized, lead-lined or thick-walled plastic containers that limit radiation emission. The container should be clearly labeled as radioactive material. It should be kept away from areas of constant human presence, especially bedrooms and living rooms. Display should be behind thick acrylic glass or in a display case with appropriate shielding.

External references

https://en.wikipedia.org/wiki/https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FDavidite