Ulexite

Ulexite is a rarely occurring mineral from the mineral class of borates. It crystallizes in the triclinic crystal system with the chemical composition NaCa [ B5O6 (OH ) 6] • 5 H2O and sometimes developed prismatic to acicular, radial- crystals, but mostly granular, massive or fibrous aggregates of gray to white in color.

Special Features

In fibrous form and smoothness of the cut surfaces perpendicular to the mineral fiber in a position -coded fonts and images to be projected at the stone surface. Because of this property of the ulexite is also known under the name television stone or stone Television short TV stone.

Chance shows a green to yellow or blue fluorescence. Ulexite is with a Mohs hardness of 2 to 2.5, although very soft (still can be scratched with a fingernail ), but also very brittle and perfect cleavage parallel to the fibers.

Etymology and history

Ulexite was described in 1849 by the Hamburg chemist Georg Ludwig Ulex the first time and later named after him.

Classification

In the old classification of minerals according to Strunz ( 8th edition ) of the ulexite still belonged to the combined mineral class of " carbonates, nitrates, borates, " and then to the Department of " group borates ". Since the new classification of minerals according to Strunz ( 9th Edition ) borates form an independent mineral class and the ulexite can now be found in the department of "Island pentaborates " ( Neso - pentaborates ).

The classification of minerals according to Dana sorted the ulexite in the department of " Hydrated Borates Containing hydroxyl or halogen" (translated: hydrous borates with hydroxy or halogen).

Education and Locations

Ulexite formed in sedimentary dehydrating borax or salt lakes and salt marshes. Are condensation nuclei present, the mineral crystallizes from solution in a preferred growth direction. Accompanying minerals are other borate minerals.

Locations include Jujuy and Salta in Argentina; Potosí Department in Bolivia; New Brunswick, Newfoundland and Labrador and Nova Scotia in Canada; in Antofagasta, Coquimbo and in the region of Tarapacá in Chile; Qinghai and Tibet autonomous region in China; Hesse, Saarland and Thuringia in Germany; Zanjan in Iran; Atyrau in Kazakhstan; Arequipa in Peru; Serbia; Kütahya, Central Anatolia and the Marmara region of Turkey; as well as California, Nevada, and Oklahoma in the United States.

Crystal structure

Crystallizes in the triclinic crystal system ulexite in the space group with the lattice parameters a = 8.809 Å, b = 12.86 Å and c = 6.678 Å, α = 90.25 °, β = 109.1 ° and γ = 105.1 °, and four formula units per unit cell

Use

Ulexite is an important ore for the production of boron Fibrous varieties of pure white color can be processed into semi-precious stones, show the cabochon-cut the coveted cat's eye effect. However, the mineral respond to any heat-affected fragile. Already hot water can cause significant damage. The same applies to cleaning treatments with alkalis, acids, electroplating baths and ultrasound.