Jeremejevite

Chemical formula: Al₆(BO₃)₅F₃

Jeremejevite is a rare aluminum borate, valued for its perfectly formed, prismatic crystals with a characteristic blue color.

## Characteristics Jeremejevite is a rare and highly prized mineral from the borate group. It occurs as hexagonal, prismatic crystals with perfectly flat faces and terminations. Specimens with an intense, cornflower-blue color are the most sought after, although colorless, yellowish, and even violet crystals are also found. It often exhibits color zoning, with darker crystal terminations. It is a hard and relatively dense mineral, which, combined with its rarity, makes it one of the most expensive gemstones in the world. ## Physical Properties Jeremejevite is characterized by high hardness, ranging from 6.5 to 7.5 on the Mohs scale, which makes it resistant to scratching. It has a vitreous luster and is typically transparent to translucent. Its density is approximately 3.28 g/cm³, which is a relatively high value for a mineral of this composition. ## Colors and Varieties The most known and valued jeremejevites are those with colors ranging from light blue to deep cornflower blue. Colorless, pale yellow, greenish-yellow, and exceptionally rare violet specimens also occur. A characteristic feature is pleochroism – a change in color depending on the viewing direction, from colorless or light blue to a darker, azure shade. There are no named commercial varieties, and classification is based mainly on color and its intensity. ## History and Name The mineral was first described in 1883 by Augustin Damour based on specimens found at Mount Soktuy in the Transbaikal Region of Russia. The name honors Pavel Vladimirovich Eremeev (1830-1899), a Russian mineralogist, engineer, and professor, who first found crystals of this mineral in 1859. ## Uses Due to its extreme rarity, jeremejevite is primarily a mineral of collector's significance. The highest quality, transparent crystals with intense color are cut and used in the most expensive jewelry as faceted gemstones. Their price per carat can exceed that of diamonds.

Properties

Mohs hardness: 6.5-7.5
Luster: Vitreous
Streak: White
Density: 3.28-3.31
Cleavage: None
Fracture: Conchoidal to uneven
Transparency: Transparent to translucent
Crystal system: Hexagonal

Diagnostic features

## Identification Jeremejevite is most easily recognized by its characteristic crystal habit – perfectly formed, hexagonal prisms, often terminated by a flat basal pinacoid. Its blue color and strong pleochroism, visible under a polariscope or even with the naked eye when rotating the crystal, are also key features. Its high hardness (6.5-7.5) distinguishes it from many softer minerals. ## Distinguishing from Similar Minerals Jeremejevite is sometimes confused with aquamarine (a variety of beryl), topaz, and sapphire. It differs from aquamarine by its higher density and slightly different crystal form (aquamarine often has more complex terminations). It differs from blue topaz by its crystal habit and pleochroism. Sapphire is significantly harder (9 on the Mohs scale). In laboratory conditions, optical and X-ray studies enable definitive identification. ## Crystal Forms Jeremejevite crystals are almost always prismatic, with a hexagonal outline. They are usually elongated, straight, and terminated by flat basal faces. Pyramidal terminations are rarer. It occurs as single, well-formed crystals or in small groups loosely growing on the host rock.

Geological environment

## Genesis Jeremejevite is a hydrothermal and pegmatitic mineral. It forms in the late stages of crystallization in granite pegmatites, rich in aluminum and boron. It forms in rock cavities and fissures (druses), where it has space for free crystal growth. It is also found in alluvium (river sediments) as pebbles, due to its hardness and resistance to weathering. ## Mineral Associations This mineral often co-occurs with other pegmatitic minerals, such as quartz, albite (and other feldspars), tourmaline (especially schorl and elbaite), topaz, and also with rarer minerals like herderite or euclase. ## Localities The most important and historically first locality is Mount Soktuy in the Transbaikal Region of Russia. However, the most famous and globally valued gem-quality specimens come from Namibia, mainly from the Erongo region (Ameib, Goanikontes farms) and from the Eifel mountains in Germany (occurrences in volcanic rocks). Small quantities have also been found in Tajikistan (Pamir Mountains) and Myanmar (Mogok area).

Rarity

Very rare

For collectors

## Quality Criteria The most important criterion for evaluating jeremejevite quality is its color. Specimens with an intense, pure, cornflower or azure color, without gray or greenish tints, are most highly valued. The second key factor is transparency – the fewer inclusions and internal fractures, the more valuable the specimen. Crystal size and the perfection of its form – sharp edges, smooth faces, and lack of mechanical damage – also significantly increase its value. ## Market Prices Jeremejevite is one of the most expensive collector's minerals and gemstones. Prices for small, cut stones (under 1 carat) start from several hundred dollars per carat, but for stones over 1 carat, with intense color and high clarity, prices rise sharply, reaching from $2,000 to even over $20,000 per carat. Large, well-formed crystals with beautiful color can fetch tens of thousands of dollars at auctions. ## Popular Localities Blue, transparent crystals from Namibia, specifically the Erongo mountains, are by far the most sought after by collectors. They are considered the global standard of quality for this mineral. Specimens from the historical Russian locality are rarer and usually smaller and lighter in color. Unique, colorless crystals also come from the Eifel mountains in Germany.

Care and storage

## Cleaning Jeremejevite specimens should be cleaned very carefully. It is best to use lukewarm soapy water and a soft brush (e.g., a children's toothbrush). After washing, rinse thoroughly, preferably with distilled water, and dry with a soft, lint-free cloth. Ultrasonic and steam cleaning are risky and not recommended, especially for specimens with inclusions. ## What to Avoid Avoid contact with strong acids and bases, which can damage the crystal surface. The mineral is sensitive to sudden temperature changes, which can lead to internal fractures. Although relatively hard, it should be protected from impacts and contact with harder materials (e.g., diamond, corundum) to prevent scratching. ## Storage Collector specimens are best stored in separate, padded boxes or on stands in enclosed display cases to protect them from dust and mechanical damage. Jewelry with jeremejevite should be kept in separate pouches or jewelry boxes, away from other jewelry that could scratch it.

External references

https://en.wikipedia.org/wiki/https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FJeremejevite