C. B. Honcood 4* A. Wade— The Old Granites of Africa. 45: 



infrequently the rock is plagio- 

 clase granite or microcline granite. 

 " Granophyric structure has 

 not yet been observed in the Old 

 Granite. 



"Pegmatite veins are to be 

 found almost everywhere in the Old 

 Granite ; and it not infrequently 

 presents a reticulated appearance, 

 caused by the ramifications of 

 thick and thin dykes and veins of 

 pegmatite throughout its mass. 

 There is an abundance of hand- 

 some gi'aphic granite to be found 

 in the pegmatite. 



" Syenite has not yet been 

 found in the region of the Old 

 Granite. 



" Passages of the Old Granite to 

 quartz-porphyiy or related rocks 

 are not known, but here and there 

 dykes of quartz-porphyry do break 

 through the Old Granite. 



" Efiusive rocks and volcanic 

 ejectamenta •which might be con- 

 sidered as belonging to the granite 

 family are never found in the 

 region of the Old Granite. 



' ' In the Old Granite segregations 

 of the basic components from the 

 granite magma occur on a very 

 small scale and play an un- 

 important role. 



" On most places granophyric 

 structure is beautifully developed 

 in the Ked Granite, and is very 

 characteristic of this rock. 



"Veins of pegmatite have not 

 vet been found in the Red Granite. 



"Syenite occurs very frequently 

 witii the Red Granite, and often 

 that rock is entirely or partly 

 changed to pistacite-syenite. 



" In many instances the Red 

 Granite passes gradually over into 

 porphyritic forms belonging to 

 the quartz-porphyiy and felsite- 

 porphyry group. Sometimes we 

 find then true quartz-porphyry 

 ■where quartz and felspar both 

 occur as phenocrysts in a dense 

 ground - mass, more frequently 

 felsite-porphyry with large por- 

 phyritic crystals .phenocrysts) of 

 red felspar as Carlsbad twins. 



" In connection -with the Red 

 Granite, and at its base, resting on 

 the underlying older rocks of the 

 Pretoria Series (for instance, on 

 Mr. Pretorius' farm, Roodeplaat, 

 No. 314), distinctly stratified 

 eruptive rocks, tufts, and breccias, 

 with numerous slag inclusions 

 occur, "which certainly may be 

 considered as volcanic ejectamenta 

 of the granit-e family. They lie 

 intercalated with sheets of felsite- 

 porphyry. which represent old 

 lava streams. 



•' In the Red Granite the dark, 

 most basic components are here 

 and there segregated and separated 

 out from the magma in large aggre- 

 gates. Foremost of these occur 



