THE GEOLOGICAL FORMATION OF GERMAN S.W. AFRICA. 338 



different times. This is well shewn in the neighbourhood of 

 Warmbad. Here every possible variety of the two rocks is 

 met with, of varying- colours, coarseness of grain and proportions 

 of constituent minerals. Coarse-grained granite appears in lenti- 

 cular veins in Gneiss and in fine-grained granite. Sometimes all 

 the constituent minerals are equally developed, at others the rock 

 is distinctly porphyritic and often the Mica is entirely wanting. 

 In places segregation or fractional crystallization of the consti- 

 tuent minerals has taken place to a considerable extent. 



North- West of Warmbad is a good deal of very coarse-grained 

 rock, generally consisting of Graphic Granite with large masses 

 of Quartz often containing large crystals of Mica (Muscovite). 

 The Graphic Granite consists mostly of Felspar with incompletely 

 developed crystals of Quartz. In the largest segregations of 

 Quartz are also crystals of Felspar. This Quartz occasionally 

 sticks out like veritable reefs, except that the outline is very 

 irregular. 



Where the structure is Gneissose the several minerals often form 

 distinct bands which give the rock the appearance of a stratified 

 deposit. Such apparent anomalies as beds of Felspar and beds 

 of Mica are observed in certain localities. At one spot I noticed 

 a band of Biotite Mica about two feet thick formed of an agglo- 

 meration of crystals about one inch in diameter. 



Garnets are very plentiful all over the granite country. 



At Warmbad and other localities is a very large amount of 

 beautifully coloured Granite and Gneiss, of which the Felspar is 

 bright pink. The rock, in addition, contains a verv large pro- 

 portion of bright green Epidote (variety Pistacite) and varies 

 greatly in grain and degree of lamination. It forms a most beau^ 

 tiful ornamental stone. A somewhat similar occurrence 

 is seen at Ramans Drift (on the Orange River). Here the 

 Schist (practically a Gneiss) which was evidently formed from an 

 original sedimentary rock, contains a considerable amount of 

 Epidote in fine layers filling cracks in the original bedding planes. 

 Cracks in other directions also contain well crystallized Epidote. 

 The Schist has been upheaved by Granite, of which several veins 

 penetrate the former near the line of contact. A vein of Felsite 

 is also noticed — probably from the same Granite mass. The sur- 

 face of the Granite has copper stains at several places. 



At many localities between the Orange River and Keetmanshoop 

 one comes across traces of the original Archaean beds — Clayslates, 

 Ouartzites and Mica-Schists, — into which the Granite has been in- 

 truded, particularly where Gneiss is found. At Velloor a con- 

 siderable amoutit of Quartzite and Mica-Schist was observed. 



Intrusions of younger volcanic rocks are frequentlv met with. 

 Between Velloor and Velloors Drift several narrow dikes of Diorite 

 occur, generally running North East and South West. At Vel- 

 loor a great mass of Diorite has been intruded. This rock is 

 almost identical with the Copper-bearing Diorite of the O'okiep 

 Mine in Little Namaqualand except that the latter appears to have 

 slightly more free Quartz. 



Some Diorite intrusions are also met with North of Warmbad. 



