( 403 ) 



exceedingly rich in AI.O„. as appears sufficiently from the micros- 

 copic examination; it lias on the contrary to be looked for in the 

 glass of the groundmass. 



In the rare cases, in which after saturation of the alkalis and lime 

 an AljOj.-remaindei' shows itself, Osan.n substitutes MgO in the atom- 

 group CaAl 3 0< '), whilst Becke 5 neglects the Al 3 3 -rest in the 

 formula and mentions il separately; ii amounts here in molecular 

 proportions to 0.27. Accordingly in 1 the rock-formula is given 

 according to Osann, in 11 after Becke. In 111 and IV these double 

 values for a, c and t' after Becke have been calculated on a sum of 

 30 instead of '20 I and II). 



In the following graphic notation 1 denotes the projection of the 

 rock; the filled circle with the values of a, c, t' according t<> Osann 

 as base, (lie one not tilled with those according to Becke. 



/ yyv _ 



II. Hyalopilitic Amphiboledaeite (Amphibolephyrivitroyellowstonose). 

 From the glassy base of this greasy-shining, blackish grey rock, 

 which shows an inclination to a conchoidal fracture and in one of 

 the hand-specimens a distinct and pretty regujar separation into thin, 

 level plates from 1—7 nun. in thickness, already macroscopically 

 small plagioclases with lively microtine-habilus and glittering amphi- 

 bole-prisms arc coming forth. The very fresh, also here mostly idio- 



i) Min. Petr. Mill. XXII, 1903. Ho7. 

 2) Ibid. 215. 



