Beudantite - Encyclopedia

    Class : Sulphates, chromates, molybdates
    Subclass : Anhydrous sulphates
    Crystal System : Trigonal
    Chemistry : PbFe3(AsO4)(SO4)(OH)6
    Rarity : Rare

Beudantite is a rare mineral, present in the oxidation zone of lead deposits. It was named in honor of the French physicist and mineralogist François-Sulpice Beudant, professor of mineralogy at the University of Paris. It commonly occurs in pseudocubic rhombohedral or pseudo-octahedral crystals, in hexagonal tablets, always small in size (less than 10 mm), in grainy masses, in hummocky encrustations or in powdery coatings. It is black, dark green or brown, rarely reddish. Beudandite has a resinous to vitreous luster, and readily accompanies various arsenates (pharmacosiderite, carminite, scorodite...). It is a very accessory ore of lead.

Main photo : Beudantite from the Clara Mine, Germany © Stephan Wolfsried

Beudantite on scorodite from Upper Dumps, Viseu, Portugal © Yaiba Sakaguchi
Beudantite from Mas Dieu, Gard, France © Jean-Marc Johannet
Beudantite from Villefranche-de-Rouergue, Aveyron, France © Jean Claude Dol
Beudantite from Nuisière, Rhône, France © Pascal Chollet

Beudantite in the World

The Lavrion deposits (Greece) yielded spherical aggregates of millimetric crystals on limonite which are among the most beautiful in the world, as well as the 10 mm crystals on carminite from the Tsumeb deposit (Namibia). Good crystals with clean shapes are also known from Horhausen in Rhineland-Palatinate (Germany), Ojuela (Durango, Mexico), and Australia.

Beudantite in France

In France, beudandite forms barely millimetric crystals with adamite at Cap Garonne (Var), it is also found at Mas Dieu (Gard), at Villefranche-de-Rouergue (Haute-Vienne), at the Roffin mine near from Lachaux (Puy-de-Dôme), to Montmins (Allier), to Nuizière and Lantignié (Rhône), to Rompas (Nièvre), to Urbeis (Bas-Rhin), to Zimmerbach (Haut-Rhin), to Bussang (Vosges), Kaymar (Aveyron), etc...

Twinning and special crystallizations

No known twin known for this mineral species.

Fakes and treatments

No fake or treatment recorded for this mineral species.

Hardness : 3.5 to 4.5
Density : 4,48
Fracture : Conchoidal
Trace : Gray-yellow to gray-green

TP : Translucent to transparent
RI : 1.943 to 1.957
Birefringence : 0,014
Optical character : Uniaxial -
Pleochroism : Visible
Fluorescence : None

Solubility : Hydrochloric acid

Magnetism : None
Radioactivity : None


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