Descloizite is a rare mineral species consisting of basic
lead and
zinc vanadate, (Pb, Zn)2(OH)VO4, crystallizing in the orthorhombic system and isomorphous with
olivenite. It was discovered by A Damour in
1854, and named by him in honor of the French mineralogist Des Cloizeaux. It occurs as small prismatic or pyramidal crystals, usually forming drusy crusts and stalactitic aggregates; also as fibrous encrusting masses with a mammillary surface. The color is deep cherry-red to brown or black, and the crystals are transparent or translucent with a greasy lustre; the streak is orange-yellow to brown; specific gravity 5.9 to 6.2; hardness 31/2. A variety known as
cuprodescloizite is dull green in color; it contains a considerable amount of copper replacing zinc and some arsenic replacing
vanadium. Descloizite occurs in veills of lead ores in association with
pyromorphite,
vanadinite,
wulfenite, etc. Localities are the
Sierra de Cordoba in
Argentina,
Lake Valley in
Sierra county,
New Mexico,
Arizona,
Phoenixville in
Pennsylvania, and
Kappel (Eisen-Kappel) near
Klagenfurt in
Carinthia.
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General Information:
Chemical Formula:
PbZn(VO4)(OH)
Composition:
(Molecular Weight = 404.54 gm)
Vanadium 12.59 %
V Zinc 16.16 %
ZnHydrogen 0.25 %
H Lead 51.22 %
PbOxygen 19.77 %
O Empirical Formula:
PbZn(VO4)(OH)
Name Origin:
Named after the French mineralogist, Alfred Des Closzeaux (1817-1897).
Physical Properties:
Cleavage:
None
Color:
dark brownish black, dark reddish brown, orange red, reddish brown, or black.
Density:
6.1 - 6.2, Average = 6.15
Diaphaniety:
Transparent to Opaque
Habits:
Plumose - "Mica-like" minerals forming aggregates of plume-like forms., Tabular - Form dimensions are thin in one direction., Encrustations - Forms crust-like aggregates on matrix.
Hardness:
3.5 - Copper Penny
Luminescence:
None.
Luster:
Greasy (Oily)
Streak:
light brownish green
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