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ORTHOCLASE                           NATURAL COLOR                                 Hardness 6
Next pages     ORTHOCLASE 2    ORTHOCLASE FACET 
    17.45 cts. yellow orthoclase crystal single 

14.2 x 12 mm.

This stone is transparent. Damage at the contact zone with its bed rock, but its shape is complete

Top crystal. Enhancement: none (N)

stone PRICE  

USD 54.00 

ORIGIN: Itrongay, Madagascar

ref:Oyr1745 

 

    22.59 cts. yellow orthoclase crystal single 

16 x 16.4 mm.

This stone is transparent. Damage at the contact zone with its bed rock.

Top crystal. Enhancement: none (N)

stone PRICE  

USD 57.00 

ORIGIN: Itrongay, Madagascar

ref:Oyr2259 

 

   23.60 cts. yellow orthoclase crystal single 

18.9 x 13.9 mm.

This stone is transparent. Damage at the contact zone with its bed rock, but its shape is complete.

Top crystal. Enhancement: none (N)

stone PRICE  

USD 65.00 

ORIGIN: Itrongay, Madagascar

ref:Oyr2360 

 

   32.82 cts. yellow orthoclase crystal single 

23.5 x 18 mm.

This stone is transparent. Damage at the contact zone with its bed rock, damage at corners.

Top crystal. Enhancement: none (N)

stone PRICE  

USD 82.00 

ORIGIN: Itrongay, Madagascar

ref:Oyr3282 

 

  Enlarge  33.35 cts. yellow orthoclase crystal single 

20.2 x 15.3 mm.

This stone is transparent. Damage at the contact zone with its bed rock, cleavage on a face.

Top crystal. Enhancement: none (N)

stone PRICE  

USD 96.00 

ORIGIN: Itrongay, Madagascar

ref:Oyr3335 

 

  Enlarge  37.50 cts. yellow orthoclase crystal single 

22 x 18.7 x 9.1 mm.

Top crystal. Enhancement: none (N)

stone PRICE  

USD 159.00 

ORIGIN: Itrongay, Madagascar

ref:Oyr3750 

 

  Enlarge  42.08 cts. yellow orthoclase crystal single 

18.1 x 18.5 x 14.5 mm.

Top crystal. Enhancement: none (N)

stone PRICE  

USD 124.00 

ORIGIN: Itrongay, Madagascar

ref:Oyr4208 

 

  Enlarge  44.52 cts. yellow orthoclase crystal single 

23.4 x 19.1 x 11.4 mm.

Top crystal. Enhancement: none (N)

stone PRICE  

USD 156.00 

ORIGIN: Itrongay, Madagascar

ref:Oyr4452 

 

  Enlarge  44.84 cts. yellow orthoclase crystal single 

20 x 19.3 x 12.4 mm.

Top crystal. Enhancement: none (N)

stone PRICE  

USD 178.00 

ORIGIN: Itrongay, Madagascar

ref:Oyr4484 

 

  Enlarge  66.08 cts. yellow orthoclase crystal single 

26.9 x 21.8 x 17 mm.

Top crystal. Enhancement: none (N)

stone PRICE  

USD 238.00 

ORIGIN: Itrongay, Madagascar

ref:Oyr6608 

 

  Enlarge  66.28 cts. yellow orthoclase crystal single 

28.7 x 21.3 x 13.3 mm.

Top crystal. Enhancement: none (N)

stone PRICE  

USD 248.00 

ORIGIN: Itrongay, Madagascar

ref:Oyr6628 

 

  Enlarge  67.84 cts. yellow orthoclase crystal single 

29 x 21.7 x 11 mm.

Top crystal. Enhancement: none (N)

stone PRICE  

USD 275.00 

ORIGIN: Itrongay, Madagascar

ref:Oyr6784 

 

  Enlarge  79.89 cts. yellow orthoclase crystal single 

30.5 x 30.1 mm.

Top crystal. Enhancement: none (N)

stone PRICE  

USD 280.00 

ORIGIN: Itrongay, Madagascar

ref:Oyr7989 

 

  Enlarge  79.74 cts. yellow orthoclase crystal single 

29.2 x 22.7 x 17.4 mm.

Top crystal. Enhancement: none (N)

stone PRICE  

USD 380.00 

ORIGIN: Itrongay, Madagascar

ref:Oyr7974 

 

  Enlarge  84.06 cts. yellow orthoclase crystal single 

33.2 x 20 x 16.5 mm.

Top crystal. Enhancement: none (N)

stone PRICE  

USD 380.00 

ORIGIN: Itrongay, Madagascar

ref:Oyr8406 

 

  Enlarge  84.85 cts. yellow orthoclase crystal single 

20.7 x 22.8 x 17.5 mm.

Top crystal. Enhancement: none (N)

stone PRICE  

USD 368.00 

ORIGIN: Itrongay, Madagascar

ref:Oyr8485 

 

  Enlarge  100.35 cts. yellow orthoclase crystal single 

 34.4 x 30.6 x 20.1 mm.

Top crystal. Enhancement: none (N)

stone PRICE  

USD 445.00 

ORIGIN: Itrongay, Madagascar

ref:Oyr10035 

 

  Enlarge  102.92 cts. yellow orthoclase crystal single 

41.1 x 24 x 15.7 mm.

Top crystal. Enhancement: none (N)

stone PRICE  

USD 515.00 

ORIGIN: Itrongay, Madagascar

ref:Oyr10292 

 

  Enlarge  24 grms. yellow orthoclase crystal single 

39 x 21 x 16 mm.

Top crystal. Enhancement: none (N)

stone PRICE  

USD 690.00 

ORIGIN: Itrongay, Madagascar

ref:Oyr24g 

 

Enlarge 113.5 grms. yellow orthoclase crystal single 

77.7 x 35.3  mm.

Top crystal. Enhancement: none (N)

stone PRICE  

 SOLD 

ORIGIN: Itrongay, Madagascar

ref:Oyr113.5gr 

 

   Enlarge 60 grms. yellow orthoclase crystal single 

 50.6 x 28.2  mm.

Top crystal. Enhancement: none (N)

stone PRICE  

USD 1200.00 

ORIGIN: Itrongay, Madagascar

ref:Oyr60gr 

 

   55.50 grms. yellow orthoclase crystal single 

47.2 x 29 mm.

Top crystal. Enhancement: none (N)

Enlarge

stone PRICE  

 SOLD 

ORIGIN: Itrongay, Madagascar

ref:Oyr5550g 

 

  Enlarge  25.80 grms. yellow orthoclase crystal single 

31 x 25.2 mm.

Top crystal. Enhancement: none (N)

stone PRICE  

 SOLD 

ORIGIN: Itrongay, Madagascar

ref:Oyr2580g 

 

143 grms. yellow orthoclase crystal single 

 56 x 50.5 mm.

Top crystal. Enhancement: none (N)

Enlarge

stone PRICE  

USD 2790.00 

ORIGIN: Itrongay, Madagascar

ref:Oyr14300g 

 

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Next pages    ORTHOCLASE 2   ORTHOCLASE AFFORDABLE  ORTHOCLASE FACET 

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

Faceted  orthoclase
  
  Click on the picture to go to faceted orthoclase
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 = 116.016 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/Io): 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)AlSi3O80.5(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
Next pages    ORTHOCLASE 2   ORTHOCLASE AFFORDABLE  ORTHOCLASE FACET 
 
 
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