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Phenakite
Current inventory:  2 gems
 

Chemistry:  Be₂SiO₄  [Beryllium Silicate]

Discovered in 1833;   IMA status: Valid (pre-IMA; Grandfathered).
Phenakite was named in 1833 by Nordenkiold from the Greek word for deceiver because it was often mistaken for quartz.

Classification

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/A.01-10

8 : Silicates
A : Nesosilicates, with [SiO4]4- groups, cations of tetrahedric orientation [4]
01 : Phenakite series

Crystal Data

Crystallography:

Trigonal - Rhombohedral

Crystal Habit:

Crystals rhombohedral, tabular to prismatic, less commonly long prismatic to acicular, to 20 cm. In columnar aggregates, as spherulites, and granular.
Twinning: Penetration twins, by rotation about [0001].

Physical Properties

Cleavage:

[1120] Distinct

Fracture:

Conchoidal

Tenacity:

Brittle

Moh's Hardness:

7.5 - 8.0

Density:

2.93 - 3.00 (g/cm³)

Radioactivity:

Not Radioactive

Optical Properties

Color:

Colourless, white, yellow, pale rose

Transparency:

Transparent to Translucent

Luster:

Vitreous

Refractive Index:

1.650 - 1.670  Uniaxial ( + )

Birefringence:

0.0160

Dispersion:

0.005 (weak)

Pleochroism:

Only observed in strongly colored crystals

Occurances

Geological Setting:

In pegmatites, greisens, and alpine and hydrothermal veins.

Type Locality:

Emerald mines (Izumrudnye Kopi; Malyshevskoye deposit), Malyshevo, Ekaterinburg (Yekaterinburg; Sverdlovsk), Sverdlovskaya Oblast', Urals Region, Russia

Year Discovered:

1833

View mineral photos:

Phenakite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Phenakite is a beautiful gem that is ideal for use in jewelry because of its high hardness and bright white color. Cut gems have little fire but are very bright. Red Phenakite gems from Russia are known, but are very rare. Small gem quality crystals have been found on Pike's Peak and Mount Antero in Colorado, USA. Other sources include Burma and Madagascar.
 

  
Phenakite gems for sale: