EXPLANATION OF PLATE 8. 
Photomickogkaphs. 
Fig. 1. — The grey mineral showing high relief is the spandite. The remaindei 
is opal with black stains of manganese oxide and tlear central 
patches of chalcedony. 
FlQ. 2. — Comparatively fresh orthoclase is seen in the lower part of the photo- 
graph, and garnet in a matrix of opal with yellow stains of iron in 
the upper part. 
Fig. 3. — The apatite is white. The remainder is spandite with secondary man- 
ganese oxide. 
Fio, 4, — Spandite — white ; psilomelane — black. 
