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 Value
Highest values go to clarity, color, cutting.
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Diopside Value via Gem Price Guide
| 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 |
| Crystallography | Monoclinic. Crystals often well formed, prismatic, stubby, also massive. |
| Refractive Index | Varies by series members, 1.664-1.751 |
| 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. |
| 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 |
|
| 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
Långban, 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
Cats 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
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