Jeremejevite

Very rare mineral of the Borate Class.
Jeremejevite is quite hard and well suitable for jewellery use. However, due to its extreme rarity, it is hardly ever encountered in the gem trade.

Jeremejevite shop

jeremejewit - jeremejevite, farm ameib, namibia, 2011jeremejewit - jeremejevite, farm ameib, namibia, 2011
Two Jeremejevites mined in spring 2011
Ameib Farm, Erongo,Namibia

Origin of name: firstly described in 1883 by French mineralogist Augustin Alexis Damour, who named it in honour of Russian mineralogist, crystallographer and engineer Pawel Wladimirowich Jeremejew (1830–1899). (Source: Wikipedia.de)

Synonyms and trade names: none, but there do exist different spellings like
Jeremejewite or Yeremeyevite

Can be confused with: Jeremejevite can be colourless, yellowish and light blue to slightly purplish blue and thus can be confused with almost all other gems of similar colour. Identification is achieved by measuring physical properties e.g. refractive index.

Localities: firstly found at Mt. Soktuj (Soktuj Gora) in Russia, which is the type locality. However, this locality only yielded tiny crystals, not suitable for cutting.
There are only about a dozen known localities worldwide, six of them in Germany (Eifel) alone. Unfortunately the German sources also only produce tiny, unfacettable crystals.
The most important sources are all located in the Erongo Region in Namibia. Besides a small deposit near the town of Swakopmund it was the so-called 72 Mile deposit (72 miles north of Swakopmund on the coastal road), where the first really good Jeremejevites were found in the early 1970ies.
Since 2006 a farm called Ameib, near Usakos, occassionally yields good crystals, from which gems of fine colour and impressive size (in the case of Jeremejevite this means above 1ct) have been cut.
Jeremejewit von der Ameib Farm, Usakos, Erongo, Namibia - Jeremejevite from Ameib Farm, NamibiaJeremejewit von der Ameib Farm, Usakos, Erongo, Namibia - Jeremejevite from Ameib Farm, NamibiaJeremejewit von der Ameib Farm, Usakos, Erongo, Namibia - Jeremejevite from Ameib Farm, Namibia
Three Jeremejevites from Ameib Farm, Erongo, Namibia

Other sources are the Pantahole Mine near Momeik, Myanmar (Burma) and a deposit near the Tadjik town of Chorugh (Khorog).

Handling: Jeremejevite is quite hard, not brittle, has no cleavage and thus should be well suitable for use in jewellery. However, it is so rare that we have no empirical data from goldsmiths or setters.
According to our cutters, Jeremejevite can be cut and polished without any problems and shows no reaction to heat. It must be said, though, that the temperatures reached when dopping the stone do not exceed 60°C.
We also do not know, whether it is susceptible to acids and brines.

Because of the rarity it is almost impossible to replace Jeremejevite in case of damage. Thus we would serioulsy advise you to take it out of the setting prior to any repair jobs. We would also advise you to keep it away from acids, brines and galvanic baths and not to clean it ultrasonically.

A request to goldsmiths and setters: if you have any experience with Jeremejevite please let us know - thank You.

Worth knowing: Jeremejevite is piezoelectric.

Jeremejevite shop

Gemmological Properties of Jeremejevite

Formula:
Al6[(F,OH)3|(BO3)5]
Crystal system:
hexagonal
Mohs hardness:
6.5 to 7.5
Specific gravity:
3.28
Refractive index:
birefringent 1.640-1.653
Max. Birefringence:
0.013
Pleochroism:
colourless/ligh purplishblue
Lustre:
vitreous
Cleavage:
none
Fracture:
conchoidal
Colour:
colourless, light yellow, light blue to light violettish blue