Class

silicate mineral

Compound type

tektosilicate

Composition comments

former formula: $(Na,K)AlSiO_4$ - Common Impurities: $Mg, Ca, H_2O$

Oxides

Formula	$Na_{2}O$	$K_{2}O$	$Al_{2}O_{3}$	$SiO_{2}$
Mass fraction (%)	15.91	8.06	34.9	41.13

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.05

Dana

Major class

silicates (VIII)

Class

tectosilicate Al-Si framework (76)

Type

Feldspathoids and related species (76.02)

Group

Nepheline group (76.02.01)

Code

76.02.01.02

Phase type

crystalline

Crystal system

hexagonal

Crystal class

pyramidal

Crystal class symbol

6 (C6)

Crystal spacegroup

P6(3)

Comments

there are 3 cavities with oval outline and 1 cavity with hexagonal outline: the former are occupied by sodium, the latter by potassium

Molar mass

584.33 $g/mol$

Density

2.55 - 2.66 cal.: 2.64) $g/cm^3$

Refringence type

uniaxial

Refringence sign

negative

Birefringence

0.0030 - 0.0050

Refraction index $n_{\alpha}$

1.531 - 1.549

Refraction index $n_{\beta}$

1.528 - 1.544

Color

white, gray, brown, brownish gray, reddish white

Diaphaneity

transparent to opaque

Luster

vitreous