Colquiriite

Chemical formula: CaLiAlF<sub>₆</sub>

A rare calcium, lithium, and aluminum fluoride, forming tiny, colorless, hexagonal crystals, discovered in the Colquiri mine in Bolivia.

## Characteristics Colquiriite is a rare mineral from the halide group, specifically a complex fluoride. It occurs as small, well-formed crystals with an isometric or short prismatic habit, often with a hexagonal outline. It typically forms granular aggregates or individual crystals grown on other minerals. It is colorless or white, with a vitreous luster, which makes small specimens difficult to observe without magnification. ## Physical Properties This mineral is characterized by a relatively low hardness of 3.5 on the Mohs scale, making it susceptible to scratching. Its density is approximately 2.86 g/cm³. It is transparent to translucent, and its luster is described as vitreous. ## Colors and Varieties Colquiriite is usually colorless, rarely white. No colored varieties or trade names are distinguished. ## History and Name The mineral's name comes from its discovery locality – the Colquiri tin and zinc mine in the La Paz department, Bolivia. It was described and recognized as a new mineral species in 1980 by a team of mineralogists comprising T. Scott Ercit, Sidney A. Williams, and Frank C. Hawthorne. ## Uses Due to its extreme rarity, colquiriite has no industrial applications. It is solely an object of scientific interest and a prized acquisition for advanced systematic mineral collections.

Properties

Mohs hardness: 3.5
Luster: Vitreous
Streak: White
Density: 2.86
Cleavage: Good on {0001}
Fracture: Conchoidal
Transparency: Transparent to Translucent
Crystal system: Trigonal

Diagnostic features

## Identification Identification of colquiriite is based on its specific occurrence environment (hydrothermal veins rich in fluorine), low hardness (3.5), and characteristic form of small, hexagonal crystals with a vitreous luster. Due to the small size of the crystals and similarity to other minerals, definitive confirmation usually requires advanced analytical methods, such as chemical analysis (EDS) or X-ray diffraction (XRD). ## Distinguishing from Similar Minerals Colquiriite can be confused with other colorless minerals occurring in similar parageneses: - **Quartz:** Is significantly harder (7 on the Mohs scale). - **Fluorite:** Has similar hardness (4), but exhibits excellent cleavage in four directions (octahedral), whereas colquiriite has good cleavage in one direction. - **Cryolite:** Is very similar visually and chemically. However, cryolite has a lower density and refractive indices close to water, making it almost invisible when immersed in water. Colquiriite does not exhibit this characteristic to the same extent. ## Crystal Forms Colquiriite crystals are trigonal, but often appear as hexaoctahedra or rhombohedra. They occur as single, grown crystals or in granular aggregates.

Geological environment

## Genesis Colquiriite is a hydrothermal mineral. It forms in the late stages of crystallization in ore veins rich in tin, zinc, lithium, and fluorine. It forms by precipitation from relatively low-temperature mineral solutions. ## Mineral Associations In its type locality (Bolivia), it co-occurs with fluorite, gearksutite, sphalerite, and cassiterite. In granitic pegmatites in Colorado (USA), it is accompanied by other rare fluorides, such as cryolite, pachnolite, thomsenolite, and ralstonite. ## Localities The most important and best-documented occurrences of this mineral are: - **Bolivia:** Colquiri mine, Inquisivi Province, La Paz Department – type locality. - **USA:** St. Peters Dome area and other locations within the Pikes Peak granite batholith in El Paso County, Colorado. Most specimens available on the collector's market originate from here. - **Russia:** Rare occurrences have been reported on the Kola Peninsula.

Rarity

Very rare

For collectors

## Quality Criteria The most highly prized colquiriite specimens are those with sharp, well-formed, and transparent crystals, set on a contrasting rock matrix. Since the crystals are usually very small (millimeter-sized), their perfect form and lack of damage are crucial. Associations with other rare minerals, especially other fluorides from the Pikes Peak area, also hold significant value. ## Popular Localities The vast majority of the best collector specimens come from localities in the Pikes Peak massif in Colorado, USA. They are particularly sought after by collectors specializing in microminerals (so-called micromounts) and systematic minerals.

Care and storage

## Cleaning Colquiriite specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, they can be rinsed with distilled water and then thoroughly dried. Ultrasonic cleaners should be avoided, as they can damage delicate crystals. ## What to Avoid The mineral is soft (hardness 3.5), so it must be protected from contact with harder minerals that could scratch it. All acids and strong chemicals should be avoided. It is not sensitive to light, but sudden temperature changes should be avoided. ## Storage It is recommended to store specimens in separate, padded boxes or display cases to prevent abrasions and mechanical damage. This also provides good protection against dust.

Sources

IMA Mineral List (CNMNC)