Muséum national d'histoire naturelle _ The species

FROM : La Viesca, Asturies, Espagne
SIZE : 21 x 11 cm

This sample is composed of a blue fluorite on a crystal of white calcite which faces are striated. It measures 21 x 11 cm.

This fluorite has a light-blue color very transparent. One can notice a purple border and some pale-green zones. This is the result of a crystallographic defect : the move of a
fluorine ion from the crystal structure to an interstitial site. This is called a "Frenkel defect".

This fluorite comes from a Spanish mine: La Viesca in Asturieas. The Muséum national d’Histoire naturelle could obtain this fluorite thanks to support from Total. It is kept in the storage rooms of the collections (i.e., not yet displayed to the public).

Photography: Louis-Dominique Bayle, © MNHN.

SPECIE : Fluorite

HISTORY : Name derived from Latin "fluere" meaning flowing, in reference to its melting behavior

Species first described in 1529 by Agricola Georgius (1494-1555), German mineralogist

Type-locality: undefined because species already known by the Ancients
ANCIENT NAME : Spatum vitreum, calx fluorata, spath fluor

CHEMICAL FORMULA : Ca F2
CRYSTAL SYSTEM : Cubic
COLOR : Colorless, white, blue, green, yellow, violett, pink
DIAPHANIETY : Transparent to translucide
LUSTER : Vitreous
STREAK : White
MORPHOLOGY : Well-formed crystals, cubic-shaped, octahedrally-shaped
HARDNESS : 4
DENSITY : 3,18

CHEMICAL CLASS : III - Halogénures
GROUP : Fluorite
STRUNZ CLASS BEFORE 2001 : 3/A.08-10
STRUNZ CLASS AFTER 2001 : 3.AB.25

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MNHN N°192.18

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