Vanadinite

Vanadinit is a rarely occurring mineral from the mineral class of " phosphates, arsenates and vanadates ." It crystallizes in the hexagonal crystal system with the chemical composition Pb5 [Cl | ( VO4 ) 3] and developed in the short to long prismatic ( rarely pyramidal ) crystals, but also racemose to earthy or radiating aggregates in white, gray, yellow, orange to brown in color.

Vanadinit is a member of the apatite - pyromorphite group.

Special Features

Vanadinit heard with a Mohs hardness of 3 to the soft minerals. It melts easily before the blowpipe, and dissolves readily in nitric acid.

Etymology and history

Was first found and described Vanadinit 1838 in Zimapan in Mexico. It was named with reference to its vanadium content.

Classification

In the classification by Strunz Vanadinit is classified in the phosphates, arsenates and vanadates. It is counted among the phosphates, arsenates and vanadates with other anions, but without water of crystallization. Both in the eighth edition and ninth edition, it counts with apatite, pyromorphite and other minerals to the apatite group. In its 9th edition this is also a subgroup of phosphates, arsenates and vanadates with only large cations (OH, etc. ) and a ratio of anions and RO 4 of 0.33:1.

In the classification of minerals according to Dana it forms with pyromorphite, Mimetite and Pyromorphit a subset of Anhydrous Phosphates, etc., with hydroxyl or halogen ions and a composition (A ) 5 ( XO4 ) 3 Zq. These three minerals form with each other at least partially a mixed crystal system in which the VO4 is substituted for PO4 and AsO4 for Pyromorphit to Mimetite.

Modifications and varieties

As Endlichit or arsenic Vanadinit by a small admixtures of arsenic yellow colored variety of Vanadinit is called. What has been described Endlichit 1885 by Friedrich August Genth ( 1820-1893 ) and Gerhard vom Rath ( 1830-1888 ).

Education and Locations

Vanadinit is a secondary mineral and forms accompanied by anglesite, barite, calcite, cerussite, Mottramite, pyromorphite, Wulfenite and Goethite in lead deposits. Occasionally, it is fused with Pyromorphit or Mimetite or waxed to be found in Descloizit oriented.

Locations are in addition to its type locality in Mexico. Argentina, among others, the Black Forest in Germany, Djebel Mahseur and Mibladen in Morocco, Tsumeb in Namibia, Wanlockhead in Scotland, Gotland in Sweden, Berezovsky in Siberia, and Arizona in the U.S.

Crystal structure

Vanadinit crystallizes hexagonally in the crystal class 6 / m. the space group is P63 / m with two formula units per unit cell. The lattice constants are a = 1.0331 nm and c = 0.7343 nm, the vanadium ion is tetrahedrally surrounded by oxygen ions. The chlorine ions sit at the corners of the unit cell and at the level of C / 2 The lead busy two differently coordinated lattice sites.

Use

Vanadinit serves as raw material for the production of special steels for major alloying element vanadium.

As a gemstone Vanadinit is not to be used because of its low hardness. Occasionally, however, it is polished by collectors in cabochon form.