Vol. VIII, No. 9.} The Origin of Meteorites. 321 
[NV.S.] 
of 0°93°,, and of taenite (Fe,Ni) a decrease of 7°3°. On this 
interpretation the crystalline structures of many siderites must 
be of secondary origin, due to the formation and crystallisation 
of nickel-iron alloys on release of pressure. 
I must also refer briefly to one other case explicable in 
terms of relief of pressure, as it concerns 
a siderite containing nodules of silicates, 
and therefore approximating to the siderolites. This is the 
Kodaikanal meteoric iron. The silicate nodules have been 
found by Berwerth! to contain spherulitic aggregates of a 
mineral to which he gives the name weinbergerite, and assigns 
Weinbergerite. 
may have been derived from an original garnet (alkalibearing, 
like lagoriolite*) on release of pressure. The equation might 
Ww — 
6FeO.2(Mg,Ca)O.(Na,K),0.Al,O,.2Fe,0..9S8i0, = 
Alkali-garne 
(Na, K),0.AL.0..2S8i0, + 7(Fe,Mg,Ca)SiO, + FeO + 2Fe_0.. 
Nepheline yroxene 
The oxides of iron are seen—partly reduced to metallic iron— 
surrounding the weinbergerite. The epikamacite shell to each 
grain of nickel-iron alloy in the meteorite may be due to an 
but there is a class of objects found in river gravels in many 
countries, and known as moldavites, billitonites, and obsidianites, 
2 Uschermak’s Min. u. Petr. Mitt., XXV, pp. 179-198 (1906). 
2 ibid., XVIII, pp. 147-155 (1899). 
3 For Berwerth’s explanation of the formation of the epikamacite 
see l.c., p. 198. 
