Moydite-(Y)

Chemical formula: YB(OH)₄CO₃

Moydite-(Y) is a very rare yttrium borocarbonate, forming small, colorless crystals with a vitreous luster.

## Characteristics Moydite-(Y) is a hydrated yttrium borocarbonate, belonging to the group of rare minerals. It occurs as very small, usually not exceeding 1 mm, tabular or prismatic crystals. They are most often colorless or white and transparent, with a strong, vitreous luster. Due to its chemical composition, containing yttrium and boron, it is a mineral of scientific interest. ## Physical Properties This mineral is characterized by a hardness in the range of 3-4 on the Mohs scale. Its crystals have a vitreous luster. The density of moydite-(Y) is approximately 3.01 g/cm³. It is transparent. ## Colors and Varieties It is usually colorless to white. No named varieties of this mineral have been distinguished. ## History and Name The mineral is named in honor of Louis Moyd (1916-2005), a Canadian mineralogist and curator of collections at the Canadian Museum of Nature in Ottawa, in recognition of his contributions to mineralogy. The mineral was described and approved by the IMA in 1986. ## Uses Due to its extreme rarity and microscopic crystal sizes, moydite-(Y) has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals and scientists.

Properties

Mohs hardness
1-2
Color
Yellow, also colorless
Luster
Vitreous
Streak
Pale yellow to colorless
Density
3.133
Cleavage
{010} good; {101} poor
Fracture
Conchoidal
Transparency
Transparent
Crystal system
Orthorhombic

Diagnostic features

## Identification Identification of moydite-(Y) with the naked eye is practically impossible due to the microscopic size of its crystals. Identification requires advanced analytical techniques, such as X-ray diffraction (XRD) and chemical analysis (e.g., EDS), to confirm the composition (presence of yttrium, boron, and the carbonate group) and crystal structure. Visually, it can be suspected in paragenesis with other rare pegmatite minerals. ## Distinguishing from Similar Minerals It can be confused with other colorless, fine-grained secondary minerals found in pegmatites, such as gagarinite-(Y) or tengerite-(Y). Definitive differentiation is only possible based on laboratory analysis. ## Crystal Forms It forms short, prismatic to tabular crystals, often with a cross-section close to square or rectangular. The crystals are very small, usually not exceeding 1 mm in length.

Geological environment

## Genesis Moydite-(Y) is a secondary mineral, formed in the late stages of hydrothermal processes in complex granite pegmatites rich in rare earth elements. It forms in rock cavities and fractures as a result of the alteration of earlier yttrium-bearing minerals. ## Mineral Associations It co-occurs with other minerals typical of pegmatites, such as quartz, microcline, albite, fluorite, gagarinite-(Y), tengerite-(Y), lokkaite-(Y), and other rare earth element minerals. ## Localities The most important and type locality is the Evans-Lou quarry in Val-des-Monts, Quebec, Canada. This is the only locality from which well-characterized specimens of this mineral originate.

Rarity

Very rare

For collectors

## Quality Criteria The quality of a moydite-(Y) specimen is primarily assessed based on the size and development of its crystals, which is a rarity. Specimens with clearly visible, sharp crystals, even if microscopic in size, are most valued. Association with other rare minerals is also important, as it increases the scientific and collector's value of the specimen. ## Popular Localities The only source of collector specimens is the Evans-Lou quarry in Quebec, Canada. Specimens from this locality are considered classic for this mineral.

Care and storage

## Cleaning Moydite-(Y) specimens are extremely delicate and small, therefore mechanical or chemical cleaning is not recommended. It is safest to leave them in their original state. If cleaning is absolutely necessary, compressed air can be used from a safe distance to remove loose dust particles. ## What to Avoid Avoid contact with all chemicals, including acids and bases, which can damage the mineral. It should not be heated or exposed to sudden temperature changes. Due to its low hardness, it is very susceptible to scratches and mechanical damage. ## Storage Specimens should be stored in stable conditions, away from dust and moisture. The best solution is to place them in a sealed "micromount" box, which protects against physical damage and contamination.

External references

Sources

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