Adular
(K,Na)(S7iAl)4O8
Chemical name
Adular
Mineral name
Adular
Chemical formula
(K,Na)(S7iAl)4O8
Crystal system
monoklin
Crystal Class
Prismatic (2/m)
Space Group
C2/m
Unit cell
a [Å]:8.56
b [Å]:12.96
c [Å]:7.21
Formula units
Z=4
Mohs hardness
6 - 6.5
Density [g/cm3]
2.55 - 2.63
Cleavage
(001) perfect, (010) good
Luster
Vitreous, pearly on cleavage surfaces
Refractive Index
nα = 1.518-1.520,
nβ = 1.522-1.524,
nγ = 1.522-1.525
nβ = 1.522-1.524,
nγ = 1.522-1.525
Birefringence δ
0.004 - 0.005
