Waimirite-(Y)

Chemical formula: YF₃

Waimirite-(Y) is a rare yttrium fluoride, forming small, colorless or pale pink crystals, discovered in the Pitinga mine in Brazil.

## Characteristics Waimirite-(Y) is an yttrium fluoride belonging to the oskarssonite group. This mineral forms very small, tabular or platy crystals, reaching sizes up to 0.2 mm. It typically occurs as aggregates or as single, dispersed crystals. It is colorless or takes on a pale pink hue. ## Physical Properties Waimirite-(Y) crystals are characterized by a hardness of 5.5-6 on the Mohs scale. They have a vitreous luster and are transparent to translucent. The mineral's density is approximately 5.59 g/cm³. The streak is white. ## Colors and Varieties The mineral is most often colorless, less commonly pale pink. No varieties have been distinguished. ## History and Name The mineral's name comes from the Waimiri-Atroari people, who inhabit the area where its discovery site is located - the Pitinga mine in Amazonas state, Brazil. It was officially recognized as a new mineral by the International Mineralogical Association (IMA) in 2013 (IMA2013-088). ## Uses Due to its rarity and microscopic crystal size, waimirite-(Y) is solely an object of scientific and collector interest.

Properties

Mohs hardness: 5.5-6
Luster: Vitreous
Streak: White
Density: 5.586
Cleavage: Synthetic YF3 displays perfect cleavage on {010}
Fracture: Irregular/Uneven,Conchoidal
Transparency: Transparent,Translucent
Crystal system: Orthorhombic

Diagnostic features

## Identification Identification of waimirite-(Y) is possible almost exclusively using advanced analytical methods, such as energy-dispersive X-ray spectroscopy (EDS/EDX) or X-ray diffraction (XRD), due to its microscopic size and occurrence in association with other minerals. Visually, it is practically indistinguishable from many other colorless minerals. ## Distinguishing from Similar Minerals It can be confused with other rare-earth fluorides, such as fluorite, gagarinite-(Y), or tveitite-(Y), with which it often co-occurs. Definitive distinction requires specialized chemical and structural analysis. ## Crystal Forms It forms very small, tabular or platy crystals, often grouped into irregular aggregates.

Geological environment

## Genesis This mineral forms in the late stages of crystallization in albitized granites, particularly within pegmatites rich in rare-earth elements. It occurs in rock cavities and vugs. ## Mineral Associations Waimirite-(Y) co-occurs with minerals such as albite, microcline, quartz, fluorite, gagarinite-(Y), cancrinite, polylithionite, pyrochlore, xenotime-(Y), and bastnäsite-(Y). ## Localities The only confirmed locality (type locality) is the Pitinga mine, located in the municipality of Presidente Figueiredo in Amazonas state, Brazil. This is one of the world's largest deposits of tin, niobium, tantalum, and rare-earth elements, associated with an albitized granite.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a waimirite-(Y) specimen primarily depends on the confirmation of its identity through analysis. Due to their microscopic size, specimens with well-formed, even if tiny, crystals that are clearly visible on the rock matrix are of the greatest value. Color contrast with surrounding minerals also enhances visual appeal. ## Popular Localities The only source of specimens is the Pitinga mine in Brazil, making it a key locality for collectors specializing in rare-earth element minerals and "micromounts."

Care and storage

## Cleaning Due to the extreme rarity and small size of the crystals, mechanical cleaning is not recommended. If absolutely necessary, compressed air can be used to remove loose dust particles. Avoid contact with water and chemicals. ## What to Avoid Avoid contact with acids and other aggressive chemicals. The crystals are brittle and susceptible to mechanical damage, so avoid ultrasonics, vibrations, and sudden temperature changes. ## Storage Specimens should be stored under stable conditions, in a sealed "micromount" box, to protect them from dust, moisture, and mechanical damage. They do not require special protection from light.

External references

https://www.mindat.org/min-46049.html