326 Y. KIKUCHI 



The composition of the mineral may probably be represented 

 thus : — 



Oxygen-i'atio. 



Si0 2 4S-95% 26-10 5-2 



Al,0 3 32-71...... 15-24 3 



FeO(MnO) 0-98 2-21) 



1 \ 5'55 ...1*1 



MqO(CaO) 8-36 3*34 



100-00 

 Thus we have 

 ti MgO • Î FeO • 2. ALO, • 5 810,=$ MgO ' 4 FeO ' 10 AW, • 25 SiO,, 

 which requires the following percentage composition : — 



s;n 2 49-05% 



Ah0 3 . 33-68 



FeO 9-42 



MgO 7-85 



100-00 

 Hardnesss=7. Specific gravity=2-642, a mean of several ob- 

 servations as determined by the Thoulet's solution. A thin splinter 

 fuses at the edge to a transparent globule, and gives a blue colour on 

 being" moistened with cobalt-solution and then ignited. 



Alteration — It is a significant fact that Cordierite is a mineral 

 which is easily subject to alteration at the surface of the earth ; so that 

 we know more of the altered products in various modifications from 

 different localities than of the unaltered mineral. The heterogeneous 

 outward appearances presented by these products have created many 

 ill-defined names, such as Praseolite, Aspasiolite, C.hlorophyllite, 

 Fahl unite, Gigantolite, Finite tvc. The final product of alteration 

 is that usually known as Finite, a pseudomorph consisting of 



