Eggletonite

General Information:
 Chemical Formula:
Na2Mn8[Si11AlO29](OH)7·11(H2O)
 Composition:
(Molecular Weight = 1,602.61 gm)
Sodium 2.87 % Na
Manganese 27.42 % Mn
Aluminum 1.68 % Al
Silicon 19.28 % Si
Hydrogen 1.82 % H 
Oxygen 46.92 % O 
 Empirical Formula:
Na2Mn2+8Si11AlO29OH7·11(H2O)
 Environment:
Miarolitic cavites in nepheline syenite. Probably isostructural with ganophyllite.
 IMA Status:
Approved IMA 1982
 Locality:
Big Rock Quarry, Little Rock, Pulaski County, Arkansas, USA.
 Name Origin:
Named for R. A. Eggleton, Australian National University.
Physical Properties:
 Cleavage:
[001] Perfect
 Color:
golden brown.
 Density:
2.76
 Habits:
Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite), Acicular - Occurs as needle-like crystals., Prismatic - Crystals Shaped like Slender Prisms (e .g. tourmaline).
 Hardness:
3-4 - Calcite-Fluorite
 Luster:
Vitreous (Glassy)
 Streak:
light brown
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