Mineral Information and Data:

Phenakite
Be2SiO4 [CNMNC approved formula]

Named in 1834 by Nordenskiold from the Greek for "deceiver" in allusion to its being mistaken for quartz.

IMA status : Valid species (Pre-IMA 1834) Grandfathered
CLASSIFICATION 
Dana
(8th edition) :
51.01.01.01  
  (51) Nesosilicate Insular SiO4 Groups Only
  (51.01) with cations in [4] coordination
  (51.01.01) Phenakite group
  
Nickel-Strunz
(10th edition) :
09.AA.05
  (09) Silicates
  (09.A) Nesosilicates (Isolated tetrahedron) structures
  (09.AA) Nesosilicates without additional anions; cations in tetrahedral [4] coordination
  
Crystal system: Trigonal System
Point group (H-M): 3 — rhombohedral
Unit cell: a = 12.47 Å, c = 8.25 Å
Crystal Habit: Crystals rhombohedral, prismatic or sometimes long prismatic to acicular, granular, acicular columnar aggregates
Twinning: About [0001] axis, penetration
  
Color: Colorless, yellow, pink, pinkish red, brown, bluish
Diaphaneity: Transparent
Luster: Vitreous
Hardness (Mohs): 7.5 to 8
Measured Density: 2.93 to 3.0 g/cm3
Cleavage: 2; {1120} distinct, {1011} imperfect
Tenacity: Brittle
Fracture: Conchoidal
  
Geologic Setting: In pegmatites, greisens, and alpine and hydrothermal veins.
Mineral Association: Topaz, beryl, chrysoberyl, fluorite, muscovite, quartz
  
Synonyms/varieties: Phenacite
Other Properties: Gemstone Readily Available.
Comments: Bright blue cathodoluminescence

 

Phenakite
Origin: Mt. Antero, Chaffee Co., Colorado, U.S.A.
Sample size: Microscopic image
Photo and Owner: Lou Perloff

 

Phenakite
Lustrous, gemmy, colorless rhombic crystals of phenakite on a feldspar and muscovite matrix.
Origin: Mt. Antero, Chaffee County, Colorado, U.S.A.
Sample size: 7.8 x 7.5 x 4.0 cm
Photo: Rob Lavinsky

 

Phenakite
(zoom-in of above)

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