Barite in the sedimentary cover

(Redoutières quarry)

The barite (or baryte*) mined in Chaillac's open-cast mines (quarries) comes in various colours, textures and crystals.

(* international nomenclature recommends an "ite" ending for most minerals).

Barite is found at the base of the series in the coarse facies of the conglomerate and the coarse sandstones in pure white cement. These sandstones with barytic cement show their original colour at this level because they have been preserved from oxidation: iron is present in the form of sulfides, as in the Rossignol vein.

Driftwood (tree trunks), largely epigenized (replaced) by barite, is found in these facies.

Ribboned "veins" characterise some areas above the Rossignol vein: solutions migrate in cracks less well organised than in the fault network of the crystalline basement and locally flow along subhorizontal drains parallel to the sedimentary layers. Oxidation occurs later above the first clay lenses, and the ribbon-like crystallisations of barite and fluorite take a rusty colour.