284 



Report S.A.A. Advancement of Science. 



forms veins running through the granite in places, and fluorspar oc- 

 curs in deep blue crystals in a similar way. Molybdenite occurs in 

 a quartz segregation vein near Glenville, about three miles from 

 Bulawayo. 



"•■'""SI .^ 



MATol'O (IKAMTE 



Several nf ihe granites from Northern Rhodesia contain orthite 

 (allanite). This mineral occurs in yellowish-brown idiomorphic 

 cnstals or rounded grains. The pleochroism is not strong and the 

 double refraction scarcely exceeds that of quartz. A rock from the 

 Jiljuyi River contains numerous crystals about .5 to 1.5 mm. in length, 

 occasionally twinned, and shewing inclusions of zircon, apatite, and 

 magnetite. A granite from Kalomo shews zoned orthite surrounded 

 by epidote with crystal outline, the latter being in turn enclosed in 

 biotite. Epidote is extraordinarily abundant, and there is a good deal 

 <)f sphene. A gneissose rock from the Wankie District of Matabele- 

 land with orthoclase crystals several inches across, presents some 

 special points of interest. Little pink garnets and minute hrown 

 granules which prove to be orthite can be detected b\ the unarmed 

 eye. The garnet is in the larger grains, but the orthite is much more 

 abundant. It is more strongly pleochroic than in the rocks previously 

 mentioned, it shews zonary banding and is frequently surrounded 

 by Ijiotite. but no epidote is present. The rock C(jntains much 

 apatite. 



