Legrandite

Legrandite is a rare arsenate mineral, discovered in 1934 and named after the Belgian mining engineer Legrand. Chemically, it is a hydrated zinc arsenate hydroxide, found as a secondary mineral in zinc ores, often in association with limonite. The most notable source of the mineral is the now abandoned Ojuela mine in Durango, Mexico. It is highly praised for its vitreous rich yellow colour and is a desirable item among mineral collectors.
See more at Wikipedia.org...

General Information:
 Chemical Formula:
Zn2(AsO4)(OH)·(H2O)
 Composition:
(Molecular Weight = 304.72 gm)
Zinc 42.92 % Zn
Arsenic 24.59 % As
Hydrogen 0.99 % H 
Oxygen 31.50 % O 
 Empirical Formula:
Zn2(AsO4)(OH)·(H2O)
 Environment:
Secondary mineral in zinc orebodies.
 Locality:
Ojuela mine near Mapimi, Durango.
 Name Origin:
Named after the Belgian mining engineer, Legrande.
Physical Properties:
 Cleavage:
[100] Imperfect
 Color:
yellow or yellowish orange.
 Density:
4
 Diaphaniety:
Translucent
 Habits:
Crystalline - Fine - Occurs as well-formed fine sized crystals., Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).,
 Hardness:
4-5 - Fluorite-Apatite
 Luster:
Vitreous (Glassy)
 Streak:
white
More details...