Villiaumite

Villiaumit, chemically sodium fluoride, is a rarely occurring mineral from the mineral class of halides. It crystallizes in the cubic crystal system with the chemical composition NaF and most forms grains or masses, rarely cubic crystals up to 15 cm of dark red, pink, or orange.

Special Features

Viliaumit is water soluble, the solubility increases with temperature. Under UV light it fluoresces dark red, orange or yellow.

Etymology and history

The mineral was first found in 1908 by Maxime Villiaume on the belonging to the Îles de Los island Roume in Guinea and examined by Antoine Lacroix and scientifically described. The mineral was named after Villiaume.

Classification

In the classification of minerals according to Strunz Villiaumit is classified in the simple halides. In the 8th edition it made with Carobbiit, Chlorargyrite, Griceit, halite, sylvite and Bromargyrit a group. In the 9th edition it forms with Carobbiit, Griceit, halite and sylvite a subset of the simple halides without crystal water and a ratio of metal to halide of 1:1 or 2:3.

In the classification of minerals according to Dana it forms with Carobbiit, Griceit, halite and sylvite the Halitgruppe, a subgroup of the anhydrous and hydrous halides with the formula AX.

Education and Locations

Villiaumit forms in nepheline syenites from the reaction of nepheline, aegirine and fluorine to Villiaumit, albite, magnetite and oxygen. Quartz, however, prevents the formation of Villiaumit. Rarely is also formed in dried-up salt lakes.

In addition to the type locality Villiaumit world was so far to about 30 other localities (as of 2010) have been found. These include Poços de Caldas in Brazil's Minas Gerais State, Lajemmerais and Rouville, Quebec City (Canada), Kvanefjeld at Narsaq to Greenland, the Lake Magadi in Kenya, Aris in Namibia, Nome, Norway, the Chibinen and the Lovozero Mountains in Russia and Jamestown and Spinger in the United States.

Crystal structure

Villiaumit crystallizes in the cubic crystal system in the space group Fm3m with lattice parameters a = 4.634 Å and four formula units per unit cell.

Precautions

Sodium fluoride is toxic if swallowed. Does it come with acids in contact to toxic hydrogen fluoride forms.