A CONTRIBUTION TO THE PETROGRAPHY OF BENGUELLA. 559 



Fig. 3. Hornfelsed porphyry, Bailundo. Ordinary light, x 15. A recrystallised granulitic quartzo- 

 felspathic groundmass, which contains irregular clots of intergrown hornblende, biotite, magnetite, and 

 occasionally cassiterite ; and cloudy phenocrysts of felspar (orthoclase and oligoclase). 



Eig. 4. Shonkinite, Ochilesa. Ordinary light, x 15. Shows pseudo-porphyritic euhedral crystals of 

 barkevikite (centre), and titanaugite (south-eastern quadrant), in a groundmass consisting of orthoclase, and a 

 little sodalite which is not distinguishable in the photograph. The felsic minerals contain numerous small 

 inclusions of titanaugite and barkevikite, and apatite is enclosed within the coloured minerals. 



Fig. 5. Solvsbergite-vitrophyre, Chieuca. Ordinary light, x 24. Shows small phenocrysts of aegirine. 

 augite and magnetite (centre of field), in colourless glassy groundmass crowded with microlites of aegirine. 



Fig. 6. Ouachitite, Ochilesa. Ordinary light, x 15. Shows numerous small euhedral sections of green 

 augite, and large plates of bleached biotite (centre of field), in groundmass of calcite (colourless areas), and a 

 little melilite (?) which cannot be distinguished in the photograph. The irregular black sections are of blue 

 translucent auatase which has been derived by the alteration of ilmenite. 



