Burtite

Chemical formula: CaSn<sup>4+</sup>(OH)<sub>6</sub>

Burtite is a rare calcium-tin hydroxide, distinguished by its regular, colorless or pale yellow crystals with a strong, almost adamantine luster.

## Characteristics Burtite is a rare mineral from the hydroxide group, chemically classified as a calcium-tin hydroxide. It forms very well-developed, single crystals with an isometric habit, most often in the form of rhombic dodecahedra or octahedra, as well as combinations thereof. Crystals are usually small, rarely exceeding a few millimeters. A characteristic feature of burtite is its very strong luster, described as adamantine or resinous, which gives it a unique appearance, even at small sizes. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of 3. It is transparent, and its density is approximately 3.31 g/cm³. It exhibits perfect cleavage in three directions, parallel to the faces of a cube {001}. ## Colors and Varieties Burtite is most often colorless, but can also be pale yellow or light brown. No color or commercial varieties are distinguished. ## History and Name The mineral was described in 1980 by G.A. Desborough, J.E. Taggart Jr., and E.L. Munson. Its name honors Donald M. Burt (born 1948), a professor of geology at Arizona State University, in recognition of his contributions to the study of skarn mineralogy – the environment in which burtite is found. ## Applications Due to its rarity and small crystal size, burtite has no industrial applications. It is solely an object of interest for collectors of rare minerals and scientists.

Properties

Mohs hardness
3
Luster
Adamantine to Resinous
Streak
White
Density
3.31
Cleavage
Perfect on {001}
Transparency
Transparent
Crystal system
Cubic

Diagnostic features

## Identification The key features for identifying burtite are its characteristic, regular crystal forms (dodecahedra and octahedra), very strong, adamantine luster, and low hardness (3 on the Mohs scale). Its occurrence environment – tin-bearing skarns – is also an important indicator. ## Distinguishing from Similar Minerals Burtite can be confused with some colorless or pale yellow garnets (e.g., grossular), which occur in similar environments. However, garnets are significantly harder (hardness 6.5-7.5). It differs from cassiterite (a tin mineral) by its much lower hardness (cassiterite has a hardness of 6-7). From scheelite, with which it may co-occur, it differs by its lower density and the lack of the intense UV fluorescence characteristic of scheelite. ## Crystal Forms Burtite crystallizes in the isometric system, forming well-developed, equant crystals. The dominant forms are the rhombic dodecahedron {110} and the octahedron {111}. Crystals usually occur as single, overgrown on the surface of other minerals, less often in the form of small aggregates.

Geological environment

## Genesis Burtite is a hydrothermal mineral. It forms in contact zones between granitoid intrusions and carbonate rocks (limestones or dolomites), within so-called calc-skarns. Its crystallization is associated with the metasomatic interaction of tin-rich solutions with calcium-rich rocks. ## Mineral Associations This mineral occurs in association with other minerals typical of skarns. Its most common associations include: andradite (garnet), wollastonite, diopside, vesuvianite, malayaite, as well as tin ore minerals such as cassiterite. ## Localities The most important and type locality for burtite is the Pinyok mine in Pattani Province, Thailand, from which the best-known specimens originate. Other confirmed localities include the Veta Cotaje deposit in the Potosí Department, Bolivia, the area around Brooks Peak in New Zealand, and some tin deposits in Russia (e.g., in the Komsomolsk region in the Russian Far East).

Rarity

Very rare

For collectors

## Quality Criteria The most highly valued burtite specimens are those with sharp, fully developed, and undamaged crystals of high transparency and strong luster. Ideal crystals have the form of textbook dodecahedra or octahedra. An additional advantage is their placement on a contrasting rock matrix, e.g., in association with dark-colored garnets. Due to the rarity of the mineral, even small but well-formed crystals are sought after by collectors. ## Popular Localities The Pinyok mine in Thailand is considered the classic and most desirable locality for burtite. Specimens from this location serve as the standard for the species and are the most highly valued in the collector's market.

Care and storage

## Cleaning Burtite is a soft and brittle mineral, therefore it requires delicate handling. For removing dust and loose impurities, it is best to use a soft brush. If necessary, the specimen can be rinsed in distilled water. Ultrasonic cleaners should be avoided, as they could damage the crystals. ## What to Avoid Protect the mineral from contact with harder materials to avoid scratches (Mohs hardness 3). As a hydroxide, it may be sensitive to acids. It is stable under normal conditions and is not sensitive to sunlight or temperature changes in household environments. ## Storage It is recommended to store burtite specimens in separate, padded boxes or display cases to prevent abrasions and mechanical damage. It should not be stored in contact with harder minerals, such as quartz or fluorite.

Sources

Read more