Zincalstibite
Zincalstibite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Zn₂Al(OH)₆[Sb(OH)₆].
It crystallizes in the hexagonal crystal system (space group R-3). It is a member of the Hydrotalcite structural group.
Key properties: White streak; Vitreous luster; optically uniaxial.
IMA symbol Zas, IMA status: approved, named in 1998.
Found in cavities in marble likely an alteration product of different sulfides (sphalerite, zinkenite, stibioluzonite) by low-temperature Al-rich hydrothermal fluids (1T).
It is found associated with Mimetite, opal, an amorphous copper-silicate phase (1T); cyanophyllite, linarite, baryte, quartz, goethite (9R).
The name refers to the composition, as a mineral with essential zinc, and structurally related to cualstibite.