Mineralogy Database

Orthoclase Mineral Data

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General Orthoclase Information

Help on Chemical Formula: Chemical Formula: KAlSi3O8
Help on Composition: Composition: Molecular Weight = 278.33 gm
   Potassium  14.05 %  K    16.92 % K2O
   Aluminum    9.69 %  Al   18.32 % Al2O3
   Silicon    30.27 %  Si   64.76 % SiO2
   Oxygen     45.99 %  O
             ______        ______ 
             100.00 %      100.00 % = TOTAL OXIDE
Help on Empirical Formula: Empirical Formula: KAlSi3O8
Help on Environment: Environment: Intrusive and extrusive igneous, and metamorphic rocks.
Help on IMA Status: IMA Status: Valid Species (Pre-IMA) 1823
Help on Locality: Locality: Common world wide occurrences. Link to MinDat.org Location Data.
Help on Name Origin: Name Origin: From the Greek orthos - "right" and kalo -" I cleave" in allusion to the mineral's right angle of good cleavage.
Help on Name Pronunciation: Name Pronunciation: Orthoclase + Pronunciation Say ORTHOCLASE
Help on Synonym: Synonym: Adularia
  Orthose
 

Orthoclase Image

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  Lorenzenite   Orthoclase

Comments: Striated, dark violet crystal of lorenzenite in cream-colored orthoclase.
Location: Khibiny Massif, Kola Peninsula, Russia. Scale: 1.3 x 1.2 cm.
© John Veevaert
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  Orthoclase

Comments: Carlsbad twinned crystal of orthoclase. Former Martín Oliete Fontela collection.
Location: Zarzalejo, Madrid. Scale: 5.2x4.6x2.2 cm.
© Fabre Minerals
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  Orthoclase

Comments: Gemmy, twinned adularia (orthoclase) specimen on matrix. Former Bally Museum collection.
Location: Rhonegletscher, Switzerland. Scale: Crystal size 3 x 2 cm.
© Fabre Minerals

Orthoclase Crystallography
Help on Axial Ratios: Axial Ratios: a:b:c =0.6636:1:0.5534
Help on Cell Dimensions: Cell Dimensions: a = 8.625, b = 12.996, c = 7.193, Z = 4; beta = 116.016° V = 724.57 Den(Calc)= 2.55
Help on Crystal System: Crystal System: Monoclinic - Prismatic H-M Symbol (2/m) Space Group: C 2/m
Help on X Ray Diffraction: X Ray Diffraction: By Intensity(I/Io): 3.18(1), 4.02(0.9), 3.8(0.8),
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Forms: ( 1 1 0) ( 1 0 1) ( 0 0 1) ( 0 1 0)

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Physical Properties of Orthoclase

Help on Cleavage: Cleavage: {001} Perfect, {010} Good
Help on Color: Color: Colorless, Greenish, Grayish yellow, White, Pink.
Help on Density: Density: 2.56
Help on Diaphaneity: Diaphaneity: Transparent to translucent
Help on Fracture: Fracture: Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern.
Help on Habit: Habit: Blocky - Crystal shape tends to be equant (e.g. feldspars).
Help on Habit: Habit: Massive - Granular - Common texture observed in granite and other igneous rock.
Help on Habit: Habit: Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).
Help on Hardness: Hardness: 6 - Orthoclase
Help on Luminescence: Luminescence: Non-fluorescent.
Help on Luster: Luster: Vitreous (Glassy)
Help on Streak: Streak: white
 

Optical Properties of Orthoclase

Help on Gladstone-Dale: Gladstone-Dale: CI meas= 0.011 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.007 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2044,KPDmeas= 0.2036,KC= 0.2058
Ncalc = 1.52 - 1.53
Help on Optical Data: 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.
Help on Pleochroism (x): Pleochroism (x): colorless.
Help on Pleochroism (y): Pleochroism (y): colorless.
 

Calculated Properties of Orthoclase

Help on Electron Density: Electron Density: Bulk Density (Electron Density)=2.53 gm/cc
note: Specific Gravity of Orthoclase =2.55 gm/cc.
Help on Fermion Index: Fermion Index: Fermion Index = 0.01
Boson Index = 0.99
Help on Photoelectric: Photoelectric: PEOrthoclase = 2.85 barns/electron
U=PEOrthoclase x relectron= 7.20 barns/cc.
Help on Radioactivity: Radioactivity:

GRapi = 200.97 (Gamma Ray American Petroleum Institute Units)
Concentration of Orthoclase per GRapi unit = 0.50 (%)

Estimated Radioactivity from Orthoclase - barely detectable

 

Orthoclase Classification
Help on Dana Class: Dana Class: 76.01.01.01 (76)Tectosilicate Al-Si Framework
  (76.01)with Al-Si frameworks
  (76.01.01)K (Na,Ba) feldspars
 
76.01.01.01 Orthoclase KAlSi3O8 C 2/m 2/m
 
76.01.01.02 Sanidine (K,Na)(Si,Al)4O8 C 2/m 2/m
 
76.01.01.03 Hyalophane (K,Ba)Al(Si,Al)3O8 C 2/m 2/m
 
76.01.01.04 Celsian BaAl2Si2O8 I21/c 2/m
 
76.01.01.05 Microcline KAlSi3O8 C1 1
 
76.01.01.06 Anorthoclase (Na,K)AlSi3O8 C1 1
 
76.01.01.07 Rubicline! (Rb,K)AlSi3O8 P1 1
 
76.01.01.08 Filatovite! K[(Al,Zn)2(As,Si)2O8] I2/c 2/m
Help on Strunz Class: Strunz Class: 09.FA.30 09 - SILICATES (Germanates)
  09.F - Tektosilicates without Zeolitic H2O
  09.FA -Tektosilicates without additional non-tetrahedral anions, (Al,B):Si = 1:1
 
09.FA.30 Buddingtonite (NH4)AlSi3O8•0.5(H2O) P 21 or P 21/m Mono
 
09.FA.30 Celsian BaAl2Si2O8 I21/c 2/m
 
09.FA.30 Anorthoclase (Na,K)AlSi3O8 C1 1
 
09.FA.30 Hyalophane (K,Ba)Al(Si,Al)3O8 C 2/m 2/m
 
09.FA.30 Orthoclase KAlSi3O8 C 2/m 2/m
 
09.FA.30 Microcline KAlSi3O8 C1 1
 
09.FA.30 Rubicline! (Rb,K)AlSi3O8 P1 1
 
09.FA.30 Sanidine (K,Na)(Si,Al)4O8 C 2/m 2/m
 

Other Orthoclase Information
Help on See Also: See Also: Links to other databases for Orthoclase :
1 - Alkali-Nuts(English)
2 - Alkali-Nuts(Francais)
3 - Am. Min. Crystal Structure Database
4 - Amethyst Galleries' Mineral Gallery
5 - Athena
6 - CalTech Mineral Spectroscopy
7 - EUROmin Project
8 - Ecole des Mines de Paris
9 - Franklin Minerals(Dunn)
10 - GeoScienceWorld
11 - Google Images
12 - Google Scholar
13 - Handbook of Mineralogy (MinSocAm)
14 - Handbook of Mineralogy (UofA)
15 - HyperPhysics
16 - MinDAT
17 - Mineral and Gemstone Kingdom
18 - Mineralienatlas (Deutsch)
19 - Minerals in Thin Sections-Humboldt State
20 - Online Mineral Museum
21 - QUT Mineral Atlas
22 - Ruff.Info
23 - Tradeshop.com - The Rainbow of Gems
24 - UCLA - Petrography Thin-Sections
25 - WWW-MINCRYST

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Orthoclase

KAlSi3O8
Dana No: 76.01.01.01 Strunz No: 09.FA.30
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