428 NATURAL HISTORY OF AFRICA. 
Cape of Good Hope, and in the ranges of moun- 
tains to the north of the peninsula of the Cape, 
where it forms the fundamental rock on which the 
sandstone rests. 
Porphyry. 
This rock, which has usually a red colour, occurs 
in Upper Egypt associated with syenite, and also 
with serpentine, limestone, and clay slate ; and 
Bruce mentions it as forming mountains in Abys- 
sinia. 
Syenite. 
This rock, which is distinguished from granite 
by the hornblende it contains as an essential ingre- 
dient, occurs along with porphyry, granite, and 
other rocks in Upper Egypt, and extends south- 
ward into Abyssinia. 
Greenstone. 
Greenstone, which is a compound of hornblende 
and felspar, occurs in beds in Upper Egypt. It is 
sometimes porphyritic, and frequently it forms an 
uniform green coloured basis, in which pale green 
crystals of felspar are imbedded, forming a beauti- 
ful rock, known under the name of green porphyry. 
It is known to artists under the name antique green 
porphyry r , and it has been frequently confounded 
with the verd antique, which is a mixture of serpen- 
tine and marble, and therefore a very different rock 
from porphyry. 
