F. P. Mennell — The Somabuln Diamond Field of Rhodeaia. 459' 



Quarries. Characteristic fossils : Amplexi-zaphrentis, Zithostrotion 

 irregulare, L.Junceum, L. Portloclci, Spirifer bisulcatus, S. triangularis, 

 S. trigonalis. 



5. The uppermost beds, vvhicli in all probability were not 

 deposited over the whole of this Carboniferous area (p. 394), are seer* 

 at Trelogan, Gorsedd, HoUoway, Waenbrodlas, Eglwyseg ridge, 

 and Treflach Wood Quarries. Characteristic fossils : — 



Cyathaxonia Rushiana. Lonsdaleia Jloriformis. 



Clisiophylhim Gurkeenensis, Productus giganteus. 



Callophyllum d. F. longisinnus. 

 CampojjhyUum Murchisoni. 



6. The very highest member of the Carboniferous Limestone 

 Series are the cherty beds and their equivalent calcareous grits or 

 Cefn-y-Fedw Sandstone, as exposed near Pentre Halkyn, Hollovvay, 

 Gronant, Gorsedd, Trelogan, Prestatyn, and Graianryd. The grits 

 are characterised by the presence of abundant fish-remains in a more 

 or less fragmentary state. 



{To be concluded in our next number.) 



IV. — The Somabula Diamond Field of Ehodesia. 



By F. P. Mennell, F.G.S., Curator of the Rhodesia Museum, Bulawayo. 



rPHE last few years have inaugurated a new era in the history of 

 JL the South African diamond deposits, inasmuch as rich bodiea 

 of diamantiferous ground have been located at great distances from 

 localities which have previously been worked successfully. The 

 group of which the Premier Mine is the best known member is the 

 most striking example of this extension of area, but the centre of 

 gravity of the diamond-mining industry seems to be gradually 

 shifting northward, and the opening up of the interesting deposit of 

 the Somabula Forest, so far north of any other known occurrence, 

 foreshadows the development of an important branch of the industry 

 in the Cinderella of the South African provinces, as Ehodesia has 

 been not inaptly termed. 



No detailed or authentic description of the Somabula field has so 

 far appeared. The writer briefly referred to the occurrence of 

 a remarkable gravelly deposit west of Gwelo in his " Geology of 

 Southern Rhodesia," and ascribed its formation to the Tertiary 

 period, a course which appears fully justified by more recent and 

 detailed investigation. He had already seen diamonds and other 

 gems from the locality, but had not been made aware of their 

 source. Last year he made an examination of the ground on behalf 

 of the South African Options Syndicate, who hold a large area ou 

 the field and who have just erected plant for producing diamond* 

 on a large scale. The reports of their preliminary operations will 

 have shown that a rich deposit of good quality stones has been 

 opened up. A large quantity were disposed of at a price which 

 works out at £3 17s. per carat, and a smaller parcel sold more 

 recently' fetched £6 per OMrat. The following notes, for jiermission 

 to publish which 1 am iiideljted to the Syndicate, are intended to 



