Edenite NaCa2 (Mg; Fe2+ )5 (Si7 Al)O22 (OH)2
°
c 2001 Mineral Data Publishing, version 1.2
Crystal Data: Monoclinic. Point Group: 2=m: Commonly as well-formed prismatic crystals,
to 2.5 cm; ¯brous; as reaction rims on pyroxenes. Twinning: Simple or multiple twinning
k f100g.
Physical Properties: Cleavage: Good on f110g, intersecting at 56± and 124± ; partings on
f100g, f001g. Tenacity: [Brittle.] Hardness = [5{6] D(meas.) = 3.05{3.37 D(calc.) = 3.06
Optical Properties: Semitransparent. Color: White, gray, pale green; color zoning is
commonly seen in thin section. Luster: Vitreous.
Optical Class: Biaxial ({). Pleochroism: [Distinct, in greens, blue-greens, and yellow-browns.]
Orientation: Y = b; Z ^ c = 18± {34± . Dispersion: r > v; weak. Absorption: Z > Y > X.
® = 1.622{1.665 ¯ = 1.632{1.678 ° = 1.641{1.684 2V(meas.) = 50± {82±
Cell Data: Space Group: C2=m: a = 9.837(4) b = 17.954(6) c = 5.307(2)
¯ = 105:18(2)± Z = 2
X-ray Powder Pattern: Franklin, New Jersey, USA. (ICDD 23-1405).
3.120 (100), 8.43 (80), 3.267 (40), 2.699 (20), 2.800 (18), 3.377 (12), 9.01 (10)
Chemistry: (1) (2) (1) (2)
SiO2 50.91 50.55 Na2 O 3.40 2.35
TiO2 0.08 0.51 K2 O 0.11 0.54
Al2 O3 8.68 6.90 F 1.86
Fe2 O3 1.61 H 2 O+ 1.74 1.27
FeO 3.61 1.30 H 2 O¡ 0.17
MnO 0.12 0.07 P2 O5 0.05
MgO 19.38 22.06 ¡O = F2 0.78
CaO 10.25 13.30 Total 100.11 99.93
(1) Kotaki, Japan; corresponds to (Na0:70 K0:02 )§=0:72 (Ca1:54 Fe2+ 0:22 Na0:22 Mn0:02 )§=2:00
(Mg4:05 Al0:57 Fe2+ 3+
0:20 Fe0:17 Ti0:01 )§=5:00 (Si7:13 Al0:87 )§=8:00 O22 (OH)1:63 : (2) Franklin Marble,
Orange Co., New York, USA; by electron microprobe, F by wet chemical analysis; corresponds
to (Na0:63 K0:10 )§=0:73 (Ca1:99 Mn0:01 )§=2:00 (Mg4:58 Al0:18 Fe2+ 0:15 Ti0:05 )§=4:96 (Si7:05 Al0:95 )§=8:00
O22 [(OH)1:18 F0:82 ]§=2:00 :
Polymorphism & Series: Forms a series with ferro-edenite.
Mineral Group: Amphibole (calcic) group: Mg=(Mg + Fe2+ ) ¸ 0.5; (Na + K)A ¸ 0.5; NaB
< 0.67; (Ca + Na)B ¸ 1.34; 6.75 · Si · 7.25.
Occurrence: In intermediate plutonic igneous and medium-grade metamorphic rocks, as
amphibolites and marbles.
Association: Titanite, mica, chondrodite (Edenville, New York, USA).
Distribution: In the USA, perhaps from Edenville, Orange Co., New York, and Franklin
and Sterling Hill, Ogdensburg, Sussex Co., New Jersey. At Tory Hill, near Bancroft, and at
Wilberforce, Ontario, Canada. From Kotaki, Niigata Prefecture, Japan.
Name: For the locality at Edenville, New York, USA, although it is not certain to occur there.
References: (1) Dana, E.S. (1892) Dana's system of mineralogy, (6th edition), 386, 391.
(2) Deer, W.A., R.A. Howie, and J. Zussman (1963) Rock-forming minerals, v. 2, chain silicates,
263{314. (3) Kohn, J.A. and J.E. Comeforo (1955) Synthetic asbestos investigations, II: X-ray
and other data on synthetic °uor-richterite, -edenite, and -boron edenite. Amer. Mineral., 40,
410{421. (4) Kearns, L.E., L.E. Kite, P.B. Leavens, and J.A. Nelen (1980) Fluorine distribution in
the hydrous silicate minerals of the Franklin Marble, Orange County, New York. Amer. Mineral.,
65, 557{562.
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