EXPLANATION OF PLATE 10. 
Photomicrographs. 
Fig, 1. — Quartzite — light ; manganese-ore — black. 
Fig. 2. — The section shows piedmontite (dark) in a light-coloured matrix of 
plagioclase and orthoclase, with a certain proportion of apatite utid 
quartz. ^- 
Fii;, 3. — The black represents piedmontite, the grey is orthoclase, and the wliite 
is secondary calcite. 
Fig, 4, — The dark mineral is piedmontite and the light is calcite. 
