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    1. Microcline Value, Price, and Jewelry Information

      A cluster of microcline twinned crystals (10,0 x 9,5 cm) By Tom Epaminondas (mineral collector) and Eurico Zimbres (FGEL/UERJ) (Own work) [Public domain], via Wikimedia Commons

      Microcline

      Microcline is a variety of feldspar. The only microcline you are likely to encounter is amazonite.

      Microcline Value

      Highest values go to color, transparency, size.

      The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.

      Microcline Information

      Data Value
      Name Microcline
      Is a Variety of Feldspar
      Varieties Amazonite
      Colors White, green, blue, pink, orange
      Crystallography Triclinic
      Refractive Index 1.514-1.539
      Luster Vitreous.
      Polish Luster Greasy to vitreous.
      Fracture Luster Pearly to vitreous.
      Hardness 6-6.5
      Wearability Poor
      Fracture Uneven to splintery
      Specific Gravity 2.54-2.58
      Birefringence 0.007-0.010
      Cleavage Perfect and easy in two directions
      Stone Sizes Amazonite cabochons up to almost any size are available; the material is usually sold by the pound to hobbyists. The same applies to perthite. The Amelia material has fine color and translucency, but perfect cleavage adds fragility.
      Heat Sensitivity Yes
      Luminescence Yellow-green in LW; inert SW; green in X-ray
      Luminescence Present Yes
      Luminescence Type Fluorescent, UV-Long, X-ray Colors
      Enhancements Wax impregnation, hides fractures, common, moderately stable, detect with hot point. Irradiation, produces blue amazonite from white microcline, rare, stable, undetectable.
      Typical Treatments Fracture/Cavity Filling, Infusion/Impregnation, Irradiation
      Transparency Semitranslucent to opaque.
      UV Long Inert to weak yellowish green
      UV Short Inert
      Absorption Spectrum None distinct.
      Phenomena Aventurescence in amazonite.
      Identifying Characteristics Mottled coloring with grid like patterns
      Formula

      KAlSi3O8 (Note, this is the same formula as orthoclase, but a different crystal system.)

      Pleochroism

      None.

      Optics

      α = 1.514-1.529; β = 1.518-1.533; γ = 1.521-1.539. Biaxial (-); 2V= 66-103°.

      Optic Sign Biaxial -

      Comments

      Microcline crystals, associated with smoky quartz, are popular mineral specimens from the Pike’s Peak area of Colorado. The color of amazonite ranges from pale green to dark green and blue-green. Pinkish orthoclase is also often present as an intergrowth.

      Name

      Microcline is from Greek words meaning small and inclined because the cleavage is close to but not quite 90°.

      FELDSPAR: Microcline-amazonite, Amelia Court House Virginia, (1inch); Canada (~2 inches across)

      FELDSPAR: Microcline-amazonite, Amelia Court House Virginia, (1 inch); Canada (~2 inches across). Photo ? Joel E. Arem, PhD, FGA. Used with permission.

      Occurrence

      Microcline occurs in acidic alkali-rich plutonic rocks; also in rocks such as pegmatites, granites, syenites, and schists.

      • Pala, California; Maine: New York: North Carolina.
      • USSR; Norway; Sweden: Germany; Italy; Japan: South Africa.
      • Colorado (Pikes Peak area): amazonite.
      • Amelia Courthouse. Virginia: finest amazonite in the United States.
      • South Dakota: perthite.
      • Canada: perthite, especially Ontario and Quebec.
      • Brazil: fine amazonite.
      • India (Kashmir District): amazonite.
      • Australia (Harts Range).
      Amazonite

      Amazonite

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