Mineral Information and Data:

Edenite
NaCa2Mg5(Si7Al)O22(OH)2 [CNMNC approved formula]

Named for the locality at Edenville, New York, USA, although it is not certain to occur there. First published 1839. Name approved per nomenclature of amphiboles (IMA, 1978).

IMA status : Approved Species 1978 ()
CLASSIFICATION 
Dana
(8th edition) :
66.01.03a.10  
  (66) Inosilicate Double-Width Unbranched Chains, W=2
  (66.01) with P=2 amphibole configuration
  (66.01.03a) Group 2, the calcic amphiboles
  
Nickel-Strunz
(10th edition) :
09.DE.10
  (09) Silicates
  (09.D) Inosilicates* Structural terminology per Liebau (1985)
  (09.DE) with 2-periodic double chains, Si4O11; Clinoamphiboles
  
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Space group: C2/m
Unit cell: a = 9.83Å, b = 17.95Å, c = 5.3Å β = 105.18°
Crystal Habit: Commonly as well-formed prismatic crystals, to 2.5 cm; fibrous; as reaction rims on pyroxenes.
Twinning: Simple or multiple twinning || {100}
  
Color: White, gray, pale green; color zoning is commonly seen in thin section.
Diaphaneity: Semitransparent
Luster: Vitreous
Hardness (Mohs): 5 - 6
Measured Density: 3.05 - 3.37 g/cm3
Cleavage: Good on {110}, intersecting at 56° and 124°; partings on {100}, {001}
Tenacity: Brittle
  
Polymorphism and Series: Forms a series with ferro-edenite.
Geologic Setting: In intermediate plutonic igneous and medium-grade metamorphic rocks, as amphibolites and marbles.
Mineral Association: Titanite, mica, chondrodite (Edenville, New York, USA).
  
Other Properties: Gemstone Unlikely Available.

 

Edenite
Pale green edenite crystal with albite
Origin: Earle's Farm Fluoro-Richterite occurrence,
Wilberforce, Monmouth Township, Haliburton Co., Ontario, Canada
Sample size: 19 x 14 x 34 mm
Photo: Dan Weinrich

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