Class

silicate mineral

Compound type

tektosilicate

Comments

Low temperature dimorph of Orthoclase

Composition comments

Common replacements: Na, Ca - Common impurities: Fe, Li, Cs, Rb, H2O, Pb

Oxides

Formula	$K_{2}O$	$Na_{2}O$	$CaO$	$Al_{2}O_{3}$	$SiO_{2}$
Mass fraction (%)	16.92			18.32	64.76

Strunz

Class

silicates (09)

Division

tektosilicate without zeolitic H2O (09.F)

Family

without additional non-tetrahedral anions, (Al,B):Si = 1:1 (09.FA)

Code

09.FA.30

Dana

Major class

silicates (VIII)

Class

tectosilicate Al-Si framework (76)

Type

with Al-Si frameworks (76.01)

Group

K (Na,Ba) feldspars (76.01.01)

Code

76.01.01.05

Phase type

crystalline

Crystal system

triclinic

Crystal class

pinacoidal

Crystal class symbol

-1 (Ci)

Crystal spacegroup

P-1

Texture

monocrystalline

Molar mass

278.33 $g/mol$

Density

2.56 $g/cm^3$

Refringence type

biaxial

Refringence sign

negative

Birefringence

0.007 - 0.010

Refraction index $n_{\alpha}$

1.514 - 1.529

Refraction index $n_{\beta}$

1.518 - 1.533

Refraction index $n_{\gamma}$

1.521 - 1.539

Dispersion V

relatively weak (r > v)

Color

gray, grayish yellow, yellowish, bluish green, green, salmon-pink

Diaphaneity

transparent to translucent

Luster

vitreous