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    1. Diopside Value, Price, and Jewelry Information

      DIOPSIDE: New York (2.15), Kenya (0.75, chrome diopside), USSR (3.5, chrome diopside). Photo ? Joel E. Arem, PhD, FGA. Used with permission.

      Diopside

      Diopside Value

      Highest values go to clarity, color, cutting.

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

      Diopside Value via Gem Price Guide

      Accompanying value information:
      Chrome Diopside 1 to 2 carats 2 carats plus
      Faceted to /ct to /ct
      Black Star All sizes
      to /ct

      Diopside Information

      Data Value
      Name Diopside
      Varieties Chrome-Diopside, Lavrovite, Violane
      Colors Colorless, white, gray, pale green, dark green, blackish green, brown, yellowish to reddish brown, bright green (Cr variety); rarely blue. Schefferite is light to dark brown. Hedenbergite always dark green, brownish green, or black.
      Crystallography Monoclinic. Crystals often well formed, prismatic, stubby, also massive.
      Refractive Index Varies by series members, 1.664-1.751
      Luster Vitreous.
      Polish Luster Vitreous to resinous
      Fracture Luster Vitreous to resinous.
      Hardness 5.5 - 6.5
      Wearability Poor
      Fracture Conchoidal to uneven
      Specific Gravity Usually 3.29; range 3.22-3.38 for diopsde, higher if more Fe present.
      Birefringence Varies by series members, 0.024-0.032. See "Identifying Characteristics" below.
      Cleavage Perfect 1 direction
      Dispersion 0.017-0.020
      Stone Sizes New York material provides cutting rough of fine quality and large size. The Italian, Swiss, and Austrian diopsides are usually smaller but of fine color. Diopside from Madagascar is very dark green and less attractive, up to about 20 carats. Chrome diopsides are known up to about 10-15 carats. Most diopside localities provide material that cuts 2-10 carat gems. American Museum of Natural History (New York): 38.0 (green, New York). Smithsonian Institution (Washington, D.C): 133.0 (black, star, India); 24.1 (black, catseye, India); 19.2 (green, Madagascar); 6.8 (yellow, Italy); 4.6 (yellow, Burma).
      Heat Sensitivity No
      Luminescence Blue or cream white in SW, also orange yellow; sometimes mauve in LW. May phosphoresce a peach color.
      Luminescence Present Yes
      Luminescence Type Fluorescent, Phosphorescent, UV-Long, UV-Short
      Enhancements None known.
      Transparency Transparent to Opaque
      UV Long green, mauve
      UV Short inert, blue/white, slightly yellowish/white, orange/yellow. May phosphoresce peach.
      Absorption Spectrum Lines at 446, 493 and 505 nm. Chrome diopside, sharp lines at 490, 505, 508 nm, indistinct lines at 635, 655, 670 and double line at 690 nm. Chrome diopside has lines at 5080, 5050, 4900, plus fuzzy bands at 6350, 6550, 6700 and a doublet at 6900. Pale green diopside gives lines at 5050, 4930, and 4460.
      Phenomena Asterism, (usually 4 ray, occasionally 6) Chatoyancy
      Formula

      CaMgSi2O6.

      Complete series to CaMgSi2O6 = Hedenbergite Intermediate members = Salite, Ferrosalite

      Ferrosalite rich in Mn and Zn = Jeffersonite Diopside rich in Mn = Schefferite

      Diopside rich in Mn and Zn = Zinc Schefferite (variety)

      Diopside rich in Cr = Chrome Diopside (variety)

      Diopside color varieties include baikalite. alalite and malacolite (Pale green) and violane (purple).

      Pleochroism
      • Diopside: none
      • Jeffersonite: dark brown/light brown
      • Schefferite: dark brown/light brown
      • Hedenbergite: pale green/green brown
      • Chrome Diopside: yellow/green
      • Salite: pale green/blue-green/yellow-green
      Optics

      Biaxial (+). See “Identifying Characteristics” below.

      Optic Sign Biaxial +

      Identifying Characteristics

      Intermediate compositions have intermediate properties in the diopside-hedenbergite series; increasing iron content results in higher properties. The pleochroism of salite is: pale green/blue-green/yellow-green.

      Diopside

      Hendenbergite

      Jeffersonite

      Schefferite

      Chrome Diopside

      Optics
      a

      1.664- 1.695

      1.716 -1.726

      1.713

      1.676

      1.668-1.674

      β

      1.672 – 1.701

      1.723 – 1.730

      1.722

      1.683

      1.680

      γ

      1.695 – 1.721

      1.741 -1.751

      1.745

      1.705

      1.698-1.702

      2V

      50-60°

      52-62°

      74°

      60°

      55°

      Density

      3.22-3.38

      3.50 -3.56

      3.55

      3.39

      3.17-3.32

      Birefringence

      0.024-0.031

      0.025-0.029

      0.032

      0.031

      0.028

      Pleochroism

      none

      pale green / green-brown

      dark/light brown

      dark/light brown

      yellow/green

      Occurrence: in Ca-rich metamorphic rocks; in kimberlite (Cr-diopside).

      Burma: yellow faceted gems; also catseyes and pale green faceting material.

      Madagascar: very dark green cutting material. Sri Lanka: cuttable pebbles.

      Ontario, Canada: green faceting material.

      Quebec, Canada: red-brown material that cuts gems to 2 carats.

      Ala, Piedmont, Italy: fine green diopside (alalite is local name).

      St. Marcel, Piedmont, Italy: violet variety of diopside (violane).

      Zillerthal. Austria: fine green crystals, some transparent.

      Georgetown, California: green diopside. Crestmore, California: large crystals (non-gem).

      DeKalb, New York: fine transparent green crystals up to several inches in length.

      Slyudyanka, USSR: green crystals (baikalite or malacolite); and chrome diopside.

      Outokumpu, Finland: fine deep green Cr-diopside.

      Nammakal, India: star stones and catseyes, also dark green facetable material.

      Franklin, New Jersey: jeffersonite, schefferite, and Zn-schefterite

      L?ngban, Sweden: jeffersonite, schefferite, and Zn-schefferite.

      Kenya: chrome diopside.

      Comments: Violane has been used for beads and inlay—transparent material is always very tiny. The color of this material is deep violet or blue and is very rare. Catseye material cuts extremely sharp eyes, the best being from Burma. Faceted diopside is not extremely rare, but large (over 15 carats) clean stones are. Colors are usually dark, so a bright and attractive gem is most desirable. Hedenbergite and the intermediate varieties tend always to be opaque except in very thin splinters. Chrome diopside, quite rare in sizes over 3-4 carats, has become available in commercial quantities from the USSR. The color is excellent, with Cr content about 0.5% by weight.

      Name: Greek words meaning appearing double.

       

      Variety Names:

      Diopside, (CaMgSi2O6) runs in a solid-state series to hedenbergite, (CaFeSi2O6)

      Salite, Ferrosalite, intermediates between diopside and hedenbergite.

      Jeffersonite is ferrosalite plus Mn and Zn

      Schefferite is diopside plus Mn

      Zinc Schefferite is diopside plus Mn and Zn

      Also:

      Alalite, colorless to light green

      Cat?s Eye diopside

      Chrome diopside, deep green coloring from chromium, usually transparent

      Malacolite, light colored, translucent stones.

      Star diopside

      Violane, massive, translucent to opaque, blue/violet. Rare.

      Trade Names:

      Tashmarine, green diopside

       

      by Joel E. Arem, Ph.D., FGA

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