Best viewed using Adobe Flash Player (8 or higher).
Download hereDiscovered on July 21st 2006 in the Mont-Blanc massif located around Chamonix (France), this specimen shows a very unique combination of two minerals that are typical of the veins founded in the northern French Alps : red fluorite and smoky quartz. Apart from the exceptionnal mineralogical and esthetic qualities of this specimen, this spectacular association is now celebrated to be the first object from natural history to have been elected to as a "national treasure" usually reserved for artefacts of artistic or archeological importance. This is an unprecedented recognition for the national geological heritage of France. This specimen has been acquired thanks to the corporate philantropy of the Total company.
This sample has been baptised "Laurent" in memory to Laurent Chatel, a close friend of the discoverer of this fluorite, who unfortunately died in August 2005 during a mineralogical prospection in the French Alps.
The sample "Laurent" informs us on its crystallization conditions as well as on the geological history of the Alps. During the formation of the Alps, hydrothermal fluids have dissolved silicon, calcium and fluor from the surrounding rocks (here, a granite). Those elements will be deposited later on within cooler cracks of the granite. Silica precipitated first as crystallized quartz followed by calcium fluoride, -that is fluorite- with octahedral crystals. During the quartz and fluorite crystallization, trace amounts of aluminum and yttrium are included within the atomic structure of quartz and fluorite, respectively. Later, natural radioactivity from the surrounding rocks will progressively "activate" the color related to those trace amounts of Al and Y, namely bronze for quartz (near 225°C) and red for fluorite. Because of the Alps orogenesis and atmospheric erosion, those deeply-seated veins are getting closer to the surface before being excavated by erosion or a mineral prospector.
Photograph : Francois Farges, © MNHN
SPECIE : Fluorite
VARIETY :Fluorite
HISTORY : nom issu du latin "fluere" signifiant "sécouler", en allusion à son comportement au point de fusion.
Espèce décrite en 1529 par Agricole Georginus (1494 - 1555), minéralogiste allemand.
Localité - type : non définissable car déjà connue des Anciens
ANCIENT NAME : Spatum vitreum, calx fluorata, spath fluor
CHEMICAL FORMULA : Ca F2
CRYSTAL SYSTEM : Cubic
COLOR : Colourless, white, pink, blue, green
DIAPHANIETY : Transparent to tranluscent
LUSTER : Vitreous
STREAK : White
MORPHOLOGY : Well-formed cubic crystals, 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