La Barre mine, Puy-de-Dôme, France

It is while strolling in the forest between the small villages of La Barre and La Martinèche to the South of St-Jacques-d'Ambur in Puy-de-Dôme (France) that we find the remains of a old fluorite mine. The undergrowth is strewn with purple and green fragments and punctuated by artisanal mini-quarries made by mineral collectors. Old rusty mining tools such as wagons are slowly digested by vegetation. Massive fluorite mixed with white chalcedony is ubiquitous. It will attract the attention of any novice hiker. We can also find traces of white barite. At the bottom of the thalweg a small stream flows revealing the bright colors of fluorite and leading to 2 mine entrances blocked off by bars, partially filled with water.

Blue fluorite cubes on chalcedony

Bluegemmy fluorite cubes

Pale blue fluorite cubes on chalcedony

This mine was operated discontinuously from 1901 to 1966 and then recently secured. Almost 100,000 tonnes of fluorite were extracted for metallurgy where fluorite is used as a flux. The vein measured nearly 400 m in length for a thickness of 2 meters recognized over 40 m in height (main photo G. Mazankiewicz). He provided extraordinary samples of various shapes and colors. We thus find in the collections cubes up to 10 cm edge but also octahedra exceeding 5 cm edge and whose faces are sometimes convex. Alfred Lacroix had reported rhombododecahedra of 10 cm edge!

Blue fluorite cube with yellow heart

Yellow fluorite cubes with blue color zoning

Blue fluorite cube

Blue fluorite cube

Yellow fluorite cubes with blue color zoning

Green fluorite octahedra

The colors range from green (the dominant color of the deposit) to purple through colorless or deep blue and yellow-orange (the rarest color). Yellow and blue are reserved for cubes, which can also display both colors with spectacular color zoning. Purple is reserved for octahedra or rhombododecahedra, although some cubes may have a purple border. The crystals are usually placed on a white chalcedony with quartz microcrystals which produces very contrasting and aesthetic specimens. They may present inclusions of golden chalcopyrite.

Yellow fluorite cubes

Dark purple fluorite cubo-octahedra

Colorless fluorite cubes on chalcedony

  Références :

  • Le Règne Minéral - Special Issue N°11 2005 - Fluorites from Haute-Loire & Puy-de-Dôme