Londonite

Londonite is named after Dr. David London, Professor of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma, USA, for his contributions to the understanding of granite pegmatites.

Londonite forms colourless, white, sulfur-yellow, pale yellow, pale yellow-green crystals with vitreous lustre.

Londonite is a very rare gem - it is found only in a very limited series of pegmatites in Madagascar. Gemmy faceted material is rare.
General Information
Chemical Formula
(Cs,K,Rb)Al
 
4
Be
 
4
(B,Be)
 
12
O
 
28
Anthony et al, Handbook of mineralogy (2001)
Photos of natural/un-cut material from mindat.org
Physical Properties of Londonite
Mohs Hardness8 to 0
Anthony et al, Handbook of mineralogy (2001)
Specific Gravity3.34
Anthony et al, Handbook of mineralogy (2001)
TenacityBrittle
Anthony et al, Handbook of mineralogy (2001)
FractureConchoidal
Anthony et al, Handbook of mineralogy (2001)
Optical Properties of Londonite
Optical CharacterIsotropic
Anthony et al, Handbook of mineralogy (2001)
Colour
Colour (General)Colorless, white, sulfur-yellow, pale yellow, pale yellow-green.
Anthony et al, Handbook of mineralogy (2001)
TransparencyTransparent,Translucent
Anthony et al, Handbook of mineralogy (2001)
LustreVitreous
Anthony et al, Handbook of mineralogy (2001)
Crystallography of Londonite
Crystal SystemIsometric
Anthony et al, Handbook of mineralogy (2001)
HabitAs portions of Cs-rich material heterogenously distributed throughout crystals, patchy, exsolutionlike, and in veinlets; to 7 cm
Anthony et al, Handbook of mineralogy (2001)
Geological Environment
Where found:An uncommon component of granite pegmatites, in the central zones and in miarolitic cavities.
Anthony et al, Handbook of mineralogy (2001)
Further Information
Mineral information:Londonite information at mindat.org
Significant Gem Localities
Madagascar
 
  • Vakinankaratra
    • Betafo
      • Anosiarivo Manapa
        • Antsentsindrano
Madagascar, extraLapis English No.1, 2001, p. 55
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