Jeremejevite

Jeremejewit is a rarely occurring mineral from the mineral class of " borates " (formerly " carbonates, nitrates and borates ", see Classification ). It crystallizes in the hexagonal crystal system with the chemical composition Al6 [( F, OH ) 3 | (BO3 ) 5] and develops mostly acicular to prismatic crystals with a hexagonal habit, which are either colorless or from external additions of blue or yellow-brown color.

Special Features

Jeremejewit has piezoelectric properties, that is, by changing elastic deformation of an electrical voltage builds up as well as the known quartz crystal.

Etymology and history

First colorless crystals were found in pegmatite of Soktuj Gora in Adun - Cholon Range at Nertschinsk in the Russian region of Transbaikalia and described in 1883 by the French mineralogist Augustin Alexis Damour, of the mineral in honor of the Russian mineralogists, crystallographers and engineer Pawel wladimirowich Jeremejew ( 1830-1899) and named after this.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the Jeremejewit belonged to common mineral class of " carbonates, nitrates and borates " and then to the Department of " island borates ," where he along with Fluoborit, Karlit and Painite an independent group formed.

The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the Jeremejewit in the new class of " borates " and there in the department of "Mono borates " one. This division, however, is further subdivided by the structure of the borate complex, and the possible presence of other anions, so that the mineral according to its composition in the subsection " BO3 with additional anions; 1 (D) OH etc. can be found "where it forms the unnamed group 6.AB.15 the only member.

The classification of minerals according to Dana assigns the Jeremejewit as the old Strunz'sche systematics in the class of " carbonates, nitrates and borates ," there but in the department of " water clear borates with hydroxyl or halogen". Here he is the only member of the unnamed group 08.25.01 within the subdivision to find " Anhydrous borates with hydroxyl or halogen".

Education and Locations

Jeremejewit formed by hydrothermal processes in granitic pegmatites. Accompanying minerals include albite, tourmaline, quartz, and gypsum.

Worldwide Jeremejewit so far could be detected at 13 localities. In Germany the mineral occurred at several places in the Eifel light: On Nickenicher saddle with the calibration ( Andernach ), at the Emmelberg at Uedersdorf, on Niveligsberg Drees, am Rothenberg at Bell, on Herchenberg at Burgbrohl and the tub heads in Ochtendung.

Other localities are in addition to the type locality Soktuj Gora in Russia nor the "Panta Hole Mine" at Momeik in the Burmese Mandalay Division; Madagascar; several places in the Namibian Erongo Region and Chorugh ( Khorog ) in Tajikistan.

Morphology

Most of the intense blue Jeremejevites have no precise edges and facets. Jeremejewit crystals up to 6 cm long and about 5 mm thick, but also needle-like and about 1 mm thin. Many crystals are towards the upper end slightly narrower. Larger crystals are still sitting on the matrix, are rare. The reason for this is still unknown.

Crystal structure

Jeremejewit crystallized hexagonal space group ( Raumgruppen-Nr. 176) with the lattice parameters a = 8.56 Å and c = 8.18 Å and two formula units per unit cell.

Use as a gemstone

Jeremejewit crystals can be colorless, tan, his yellow, blue green, purple or blue. The rarest and most valuable color is a rich cornflower blue. Light or medium blue crystals are also highly sought after. Some colorless or light blue crystals go in the lower part gradually changes into a deeper blue.

As with other gemstones, the value of a Jeremejewiten depends mainly on the purity, color and weight: the most precious stones should be eye-clean or internally flawless, have an intense cornflower blue color and large (> 1 carat ) be. Jeremejevites are usually faceted baguette or emerald cut.