Glucine

Chemical formula: CaBe₄(PO₄)₂(OH)₄·₀.₅H₂O

Glucine is a rare hydrated beryllium and calcium phosphate, forming small, colorless or white crystals and aggregates.

## Characteristics Glucine is a mineral from the phosphate group, chemically classified as a hydrated basic beryllium and calcium phosphate. It occurs as very small, tabular or lath-like crystals, which rarely exceed 1 mm in length. These crystals often form radial or spherulitic aggregates, as well as thin crusts and coatings. It is a colorless to white mineral, sometimes with a yellowish or pinkish tint. ## Physical Properties Glucine crystals exhibit a vitreous or pearly luster, especially on cleavage surfaces. The mineral is transparent to translucent. Its Mohs hardness is approximately 4.5, and its density ranges from 2.39 to 2.41 g/cm³. It exhibits perfect cleavage in one direction. ## Colors and Varieties Glucine is usually colorless or white. Some specimens may have a pale yellow or pinkish hue, likely due to minor impurities. No named varieties are distinguished. ## History and Name The mineral was first described in 1963 by P.V. Pokrovsky, G.F. Turovsky, and K.V. Mirskaya based on material found in granitic pegmatites in Kazakhstan. The name "glucine" comes from the Greek word "glykys" (γλυκύς), meaning "sweet," in reference to the presence of beryllium (formerly called glucinum), whose salts often have a sweet taste. However, it should be remembered that beryllium compounds are toxic and should not be tasted. ## Uses Due to its rarity and small crystal size, glucine has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals and for scientists.

Properties

Mohs hardness: 5
Color: White, light yellow
Luster: Vitreous, Pearly
Streak: White
Density: 2.23
Cleavage: Perfect on {100}
Fracture: Fibrous,Micaceous
Transparency: Transparent,Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Glucine can be identified by its occurrence as small, tabular crystals forming radial aggregates or spherulites. Its pearly luster on cleavage planes and its occurrence in a specific geological environment – granitic pegmatites – are characteristic. Reaction with acids (solubility) is a strong diagnostic indicator, but it destroys the sample. ## Distinguishing from Similar Minerals Glucine can be confused with other white or colorless secondary minerals found in pegmatites, such as herderite, wardite, or some zeolites. It differs from herderite by its lower hardness. From wardite and zeolites, it can be distinguished by crystal habit (glucine forms tabular crystals, not typical zeolite forms) and chemical tests (if possible). ## Crystal Forms Glucine crystals are most often thin-tabular, lath-like, or platy. They usually occur as radial or fan-shaped aggregates, as well as spherulites (spherical clusters) up to several millimeters in diameter. It also forms thin crusts and coatings on other minerals.

Geological environment

## Genesis Glucine is a secondary mineral, formed by hydrothermal processes in the late stages of crystallization of granitic pegmatites. It forms in vugs and fissures, crystallizing from solutions rich in beryllium, phosphorus, and calcium, which originate from the alteration of earlier minerals such as beryl and apatite. ## Mineral Associations This mineral co-occurs with other pegmatitic minerals, especially those containing beryllium and phosphorus. The most common associations include: beryl (especially its goshenite variety), herderite, hydroxylherderite, apatite, quartz, microcline, albite, muscovite, and other rare phosphates. ## Localities The most important and classic localities for glucine are in Kazakhstan, from which the type material originates (e.g., Kara-Su, Dzhungarian Alatau Mountains). It is also known from several localities in Russia, including the Kola Peninsula (Mount Ploskaya) and the Urals. Additionally, its occurrence in small quantities has been reported in pegmatites in Brazil (Minas Gerais) and the United States (e.g., Maine).

Rarity

Very rare

For collectors

## Quality Criteria Specimens with well-formed, sharp crystals forming aesthetic, radial or spherulitic aggregates are most valued by collectors. The size of these aggregates is also important – the larger the diameter of the spherulite, the more valuable the specimen. The contrasting placement of white glucine aggregates on a darker rock matrix (e.g., on smoky quartz or microcline) significantly enhances the visual appeal and value of the specimen. Purity and lack of damage to delicate crystals are crucial. ## Popular Localities Specimens from the type locality in Kazakhstan are historically most important but rarely available on the market. Currently, samples from the Kola Peninsula in Russia are most sought after by collectors, characterized by relatively large and well-formed spherulites.

Care and storage

## Cleaning Glucine specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its reactivity with acids, only distilled water, applied in small amounts, should be used for cleaning. Ultrasonic cleaners should be avoided, as they can damage delicate crystals and aggregates. ## What to Avoid Glucine is sensitive to acids, in which it readily dissolves. It should be protected from contact with household and laboratory chemicals. It should not be heated or exposed to sudden temperature changes. Prolonged exposure to strong sunlight is not recommended, although there is no evidence of fading. ## Storage Glucine specimens, being rare and fragile, are best stored in sealed "micromount" boxes, which protect them from dust, mechanical damage, and humidity. Storage in areas with high air humidity should be avoided.