124 (?. W. Hawes— Rocks of the '' Chloritic fyrmation:' 



would be supposed, there ; 

 geodes either in the mass c 

 The analysis was made upon a specimen collectei 



Si? 



the Derby railroad "cut where there is a fine display of these 



rocks. The specimen was uniform in texture and of a light- 

 green color. 



Metadiabase, from the Dekby railroad cut. 



Silica 48-25 48-15 48^-?6 



Alumina 14-22 14-01 14-12 



Ferric oxide 1-95 2-05 2-00 



Ferrous oxide 7-39 7-43 7-41 



Manganous oxide ... 1 -30 1-19 1-24 



Lime 11-53 11-47 11-50 



Magnesia 8-26 8-11 8-19 



Soda 2-63 2-56 2-60 



Potash -24 -23 -23 



Titanic acid 1-61 1-55 1-58 



Water 2-11 2-29 2-20 



99-49 99-04 9927 



Specific gravity .-. 3-02 



The analysis, taken with the observations made upon thin 

 sections, shows that the rock is a mixture of pyroxene, chlorite, 

 labi-adorite, and titanic iron, which are the constituents of 

 diabase; and hence this metamorphic rock is appropriately 

 distinguished by the name metadiabase. The absence of car- 

 bonate of lime is noticeable, showing that in this case the 

 ohlorite was formed simultaneously with the pyroxene, and not 

 at the expense of the pyroxene, as in the case of the diabase of 

 the trap dikes of the Connecticut valley, which always contains 

 carbonate of lime as one result of the change. This rock in 

 places contains pyrite, which is also frequent in trap. 

 PoEPHTBiTic Metadiabase; South of Maltby Park. 



.48-57 48-65 



Ferric oxide -35 



Ferrous oxide 8-44 



Manganous oxide. -20 



^^a^gnesia. .--..-- ^^^ 



Potash -47 



Titanic acid 1-35 



100-44 100-51 

 Specific gravity 



