Wholesale yellow ORTHOCLASE natural gemstone faceted

General Information

Chemical Formula:

KAlSi3O8

Composition:

Molecular Weight = 278.33 gm

Potassium 14.05 % K 16.92 % K₂O

Aluminium 9.69 % Al 18.32 % Al₂O₃

Silicon 30.27 % Si 64.76 % SiO₂

Oxygen 45.99 % O

______ ______

100.00 % 100.00 % = TOTAL OxIDE

Empirical Formula:

KAlSi₃O₈

Environment:

Intrusive and extrusive igneous, and metamorphic rocks.

IMA Status:

Approved IMA 1960

Locality:

Common world wide occurrences. Madagascar

Name Origin:

From the Greek orthos - "right" and kalo -" I cleave" in allusion to the mineral's right angle of good cleavage.

Synonym:

Adularia

Orthose

Orthoclase Images

Prismatic bi-terminated crystal of orthoclase

Click on the picture to go to Orthoclase crystal.

© Image by A. Darbellay

Crystallography

Axial Ratios:

a:b:c =0.6636:1:0.5534

Cell Dimensions:

a = 8.625, b = 12.996, c = 7.193, Z = 4; beta = 116.016ø V = 724.57 Den(Calc)= 2.55

Crystal System:

Monoclinic-Prismatic H-M Symbol (2/m) Space Group: C2/m

x Ray Diffraction:

By Intensity(I/I_o): 3.18(1)4.02(0.9) 3.8(0.8)

Physical Properties

Cleavage:

[001] Perfect, [010] Good

Color:

colorless, greenish, grayish yellow, white, or pink.

Density:

2.56

Diaphaniety:

Transparent to translucent

Fracture:

Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern.

Habits:

Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline)., Massive - Granular - Common texture observed in granite and other igneous rock., Blocky - Crystal shape tends to be equant (e.g. feldspars).

Hardness:

6 - Orthoclase

Luminescence:

None.

Luster:

Vitreous (Glassy)

Streak:

white

Optical Properties

Optical Data:

Biaxial (-), a=1.518, b=1.522, g=1.523-1.524, bire=0.0050-0.0060, 2V(Calc)=52-70, 2V(Meas)=65-75. Dispersion relatively strong.

Pleochroism (x):

colorless.

Pleochroism (y):

colorless.

Pleochroism (z):

colorless.

Classification

Dana Class:

Tectosilicate Al-Si Framework

with Al-Si frameworks

(Na,Ba) feldspars

Orthoclase KAlSi3O8 C2/m 2/m

Sanidine (K,Na)(Si,Al)4O8 C2/m 2/m

Hyalophane (K,Ba)Al(Si,Al)3O8 C2/m 2/m

Celsian BaAl2Si2O8 I21/c 2/m

Microcline KAlSi3O8 C1- -1

Anorthoclase (Na,K)AlSi3O8 C1- -1

Rubicline ! (Rb,K)AlSi3O8 P1- -1

Strunz Class:

Silicates

ectosilicates (network) without anions unfamiliar to the tetraheders

STRUNZ - Silicates [Tectosilicates (network) without anions unfamiliar to the tetraheders {Feldspar group, Buddingtonite - Orthocl

Buddingtonite (NH4)AlSi3O8·0.5(H2O) P21 or P21/m Mono

Sanidine (K,Na)(Si,Al)4O8 C2/m 2/m

Microcline KAlSi3O8 C1- -1

Orthoclase KAlSi3O8 C2/m 2/m

Celsian BaAl2Si2O8 I21/c 2/m

Hyalophane (K,Ba)Al(Si,Al)3O8 C2/m 2/m

Paraselsian BaAl2Si2O8 P21/c 2/m

Slawsonite (Sr,Ca)Al2Si2O8 P21/a 2/m