Volkonskoite
Current inventory:  1 gem
 

  
Volkonskoite was named for Prince Petr Mikhailovich Volkonskii (1776-1852), Minister of the Imperial Court, Russia, patron of the natural sciences.

Discovered in 1831;   IMA status:  Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Ca_0.3(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

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/H.19-50

Nickel-Strunz 10th Ed. ID:

9.EC.40

9 : SILICATES (Germanates)
E : Phyllosilicates
C : Phyllosilicates with mica sheets, composed of tetrahedral and octahedral nets

Related to:

Smectite Group.

Members of Group:

Smectite Group: Aliettite, Beidellite, Ferrosaponite, Hectorite, Montmorillonite, Nontronite, Pimelite, Saliotite, Saponite, Sauconite, Stevensite, Swinefordite, Volkonskoite, Yakhontovite, Zincsilite

Varieties:

None

Synonyms:

Wolchonskoite

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

Fine scaly to fibrous, massive

Twinning:

None

Physical Properties

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

Optical Properties

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

Occurances

Geological Setting:

An epigenetic mineral in sandstones, conglomerates, and red beds, commonly filling voids from the decomposition of organic matter (Okhansk region, Russia); a weathering product of serpentinite (Gotse Delchev, Bulgaria).

Common Associations:

Chlorite, Tridymite

Common Impurities:

Ti, Mn, Na, K, C, P

Type Locality:

Efimyatskaya Mt, Efimyaty Village, Kama River, Okhansk, Permskaya Oblast', Middle Urals, Urals Region, Russia

Year Discovered:

1831

View mineral photos:

Volkonskoite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

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
 

  
Volkonskoite gems for sale: