Volkonskoite

Volkonskoite is a rare chromium bearing silicate mineral that is relatively soft with a Mohs hardness of only 1-2 and a waxy to dull luster. Of the few Volkonskoite sources most produce uninteresting specimens. The one source that produces beautifully colored gem quality material is Mt. Efimyatskaya in the Ural Mountains of Russia. This massive material produces specimens large enough to be used for faceting small gems. The color ranges from olive green to bright grassy green. These colors combined with the waxy luster create beautiful and unusual gems.

Distribution: On Mt. Efimyatskaya and elsewhere in the Okhansk region, middle Kama River area, Permskaya Oblast’, Ural Mountains, Russia. In the Belgorod-Dnestrovskii (Akkerman) area, Ukraine. In Bulgaria, near Gotse Delchev (Nevrokop), Pirin Mountains. Fortullino, Rosignano Marittimo, Livorno Province, Tuscany, Italy. Kleggåsen Ruby Quarry, Froland, Aust-Agder, Norway.

Chemical Formula: Ca0.3(Cr3+,Mg,Fe3+)2(Si,Al)4O10(OH)2 •4H2O
  Hydrated Calcium Chromium Magnesium Iron Silicate Hydroxide
Molecular Weight: 475.69 gm
Composition: Calcium 0.84 % Ca 1.18 % CaO
  Magnesium 4.60 % Mg 7.63 % MgO
  Aluminum 2.84 % Al 5.36 % Al2O3
  Chromium 13.12 % Cr 19.17 % Cr2O3
  Iron 3.52 % Fe 5.04 % Fe2O3
  Silicon 20.66 % Si 44.21 % SiO2
  Hydrogen 1.95 % H 17.42 % H2O
  Oxygen 52.47 % O    
    100.00 %   100.00 % = TOTAL OXIDE

 

Crystallography: Monoclinic – Prismatic
Crystal Habit: Fine scaly to fibrous, massive
Twinning: None

 

Cleavage: Perfect on {001}
Fracture: Conchoidal
Tenacity: Brittle
Moh’s Hardness: 1.0 – 2.0
Density: 2.11 – 2.36 (g/cm3)
Luminescence: Not Fluorescent
Radioactivity: Not Radioactive

 

Color: Blue-Green, bright to dark Green, grass-Green emerald-Green; emerald-Green in transmitted light
Transparency: Translucent, Opaque
Luster: Waxy, Dull
Refractive Index: 1.551 – 1.569  Biaxial ( – ) 
Birefringence: 0.018
Dispersion: Strong; r > v
Pleochroism: None