Phenakite (Phenacite)
Current inventory:  0 gems; 2 sold
 

  
Phenakite was named in 1833 by Nordenkiold from the Greek word for deceiver because it was often mistaken for quartz.

Discovered in 1833; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Be₂SiO₄

Beryllium Silicate

Molecular Weight:

110.11 gm

Composition:

Beryllium

16.37 %

Be

45.43 %

BeO

Silicon

25.51 %

Si

54.57 %

SiO₂

Oxygen

58.12 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/A.01-10

Nickel-Strunz 10th Ed. ID:

9.AA.05

9 : SILICATES (Germanates)
A : Nesosilicates
A : Nesosilicates without additional anions; cations in tetrahedral [4] coordination

Related to:

Phenakite Group.

Members of Group:

Phenakite Group: Eucryptite, Phenakite, Willemite

Varieties:

None

Synonyms:

Phenacite

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:

Distinct on {1120}, Imperfect on {1011}

Fracture:

Conchoidal

Tenacity:

Brittle

Moh's Hardness:

7.5 - 8.0

Density:

2.93 - 3.00 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Colorless, White, Yellow, Pink, Brown; may be mottled

Transparency:

Transparent to Translucent

Luster:

Vitreous

Refractive Index:

1.650 - 1.670  Uniaxial ( + )

Birefringence:

0.0170

Dispersion:

0.005 (weak)

Pleochroism:

Only observed in strongly colored crystals

Occurances

Geological Setting:

In pegmatites, greisens, and alpine and hydrothermal veins.

Common Associations:

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

Common Impurities:

None

Type Locality:

Emerald mines (Izumrudnye Kopi; Malyshevskoe deposit), Tokovaya river (Tokovaia river), Malyshevo, Ekaterinburg (Sverdlovsk), Ekaterinburgskaya (Sverdlovskaya) Oblast', Middle Urals, Urals Region, Russia

Year Discovered:

1833

View mineral photos:

Phenakite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Phenakite is a rare beryllium silicate mineral that is often found in pegmatitic pockets associated with other gem minerals such as Topaz, Emerald, Chrysoberyl and smoky Quartz. Phenakite is a beautiful gem that is ideal for use in jewelry because of its high hardness (7.5 - 8.0) 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.

Phenakite is one of the few silicate minerals that have a trigonal symmetry. This symmetry is far more common among carbonates than among silicates. Phenakite shares the same symmetry with the emerald green silicate Dioptase and the fluorescent and closely related Willemite.

Distribution: Numerous localities; some for fine crystals are: along the Tokovaya River, near Yekaterinburg (Sverdlovsk), Ural Mountains, and at Miass, Ilmen Mountains, Southern Ural Mountains, Russia. At several places around Kragerö, Norway. In France, in the Vosges Mountains, at Framont, Alsace. From near Reckingen, Valais, and many other places in Switzerland. At Leckbachrinne, Habachtal, Salzburg, Austria. In the USA, from near Florissant, El Paso County, and on Mt. Antero, Cha®ee County, Colorado; on Bald Face Mountain, North Chatham, Carroll County, New Hampshire; at Amelia, Amelia County, Virginia. In Brazil, exceptional crystals in the São Miguel de Piracicaba pegmatite, 50 km east of Belo Horizonte, and at Catuqi, Minas Gerais; in the Socotó mine, northwest of Salvador, Bahia, and elsewhere. At Klein Spitzkopje, Namibia. From Anjanabonoina, Madagascar.
 

  
Phenakite gems for sale: