Cyclo-Silicate Minerals

Mineral 4He 20Ne 40Ar (36Ar) 84Kr 130Xe 

Data are from Saito et al. (1984) unless otherwise noted. Noble gas amounts are in cm3STPg 1 and are representative values. ( ) Markov et al. (1990) magnetites were separated from Precambrian banded iron formation (BIF) in Russia. 

The mineral beryls, cordierite, and tourmaline, collectively designated as cyclosilicates, have large open channels in their crystal structures. These channels are large enough to accommodate atoms and molecules extraneous to the structure, and these minerals are well known as hosts of such extraneous elements as noble gases. Beryl and tourmaline are characteristic minerals of pegmatites, and cordierite is a common metamorphic mineral. 

Cyclo-silicates, especially beryl and cordierite, are known to have an abnormally large amount of 4He and 40Ar, which cannot be accounted for the in situ production from the radioactive decay of U, Th, and 40Ar. Lord Rayleigh (Strutt, 1908) first discovered that beryls contained excess 4He, which cannot be accounted for by in situ radiogenic 4He from U and Th. Subsequently, excesses of both 4He and 40Ar in all 

The horizontal axis denotes a distance from the left-side boundary of a beryl crystal. The right-side boundary is situated at about 4.2 mm. After Toyoda and Ozima (1988). 

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Table 5.9. Trapped noble gases in cyclo-silicate minerals and in other common crustal minerals...

E. M. Flanigen I would like to cite a recent reference on the Raman spectra of various silicates and aluminosilicates, W. P. Griffith, Raman Studies on Rock-Forming Minerals. Part I. Orthosilicates and Cyclo-silicates, J. Chem. Soc. (A) 1969, 1372. This author apparently experienced no difficulty in obtaining the Raman spectra with a He—Ne laser Raman. The particle size of the samples was not specified, but described as microcrystalline. ... 

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