Microcline Value, Price, and Jewelry Information

A cluster of microcline twinned crystals
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 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

DataValue
NameMicrocline
Is a Variety ofFeldspar
VarietiesAmazonite
Crystallography Triclinic
Refractive Index 1.514-1.539
Colors White, green, blue, pink, orange
Luster Vitreous.
Polish Luster Greasy to vitreous.
Fracture Luster Pearly to vitreous.
Fracture Uneven to splintery
Hardness 6-6.5
Specific Gravity 2.54-2.58
Birefringence 0.007-0.010
Cleavage Perfect and easy in two directions
Stone SizesAmazonite 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 SensitivityYes
Luminescence Yellow-green in LW; inert SW; green in X-ray
Wearability Poor
Enhancements Wax impregnation, hides fractures, common, moderately stable, detect with hot point. Irradiation, produces blue amazonite from white microcline, rare, stable, undetectable.
Transparency Semitranslucent to opaque.
UV LongInert to weak yellowish green
UV ShortInert
Absorption Spectrum None distinct.
Phenomena Aventurescence in amazonite.
Identifying Characteristics Mottled coloring with grid like patterns
FormulaKAlSi3O8 (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°.

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