PRIMITIVE ROCKS, 
437 
3. Mica Slate. 
This rock occurs abundantly on the banks of 
the Congo, where it appears to contain beds of 
granite, syenite, and quartz, 
4. Clai/ Slate. 
This well known mountain rock occurs abun- 
dantly in some districts in Upper Egypt, where 
it is traversed by thick veins of jasper. Captain 
' Tuckey mentions it as occurring on the banks of 
the Congo, where it is sometimes associated with 
beds of bluish grey limestone. It is an abundant 
rock in the peninsula of the Cape of Good Hope, 
and also in the great ranges of alpine land to the 
north of it, 
5. Quartz Rock, or Sandstone. 
This rock is quartz in a massive form, or in 
distinct concretions. It occurs on the banks of 
the Congo ; and part, if not all the sandstone of 
the Cape of Good Hope, belong to this species, 
6. Forj^hyry. 
This rock, which has usually a red colour, oc- 
curs in Upper Egypt in beds along with syenite, 
and sometimes also with serpentine, limestone^ 
and clay slate. Bruce mentions it as forming 
mountains in Abyssinia. 
