Photomicrographs of polished and unetched (excepting fig. 3) slabs of some 
of the ores; taken more especially to illustrate the pitted character of the 
magnetite, and the remnants of still unreplaced silicate minerals. Fig. 1 is 
ore from the Forest of Dean mine, fig. 2 ore from the Scott mine, fig. 4 
ore from the Clove mine and fig. 5 ore from the Lake mine. The silicates 
in figs. 1, 2 and 4 are represented by the corroded, gray, smoother patches. 
The pits by the black: lines, specks and small patches; the magnetite in all 
cases is white (direct reflected light). The “pits” in many cases are seri- 
citized remnants of former silicates. Fig. 3 is a polished slab of ore from the 
Canopus mine, etched with hydrochloric acid, which has attacked the mag- 
netite (rough, speckly gray), but which has not etched the ilmenite (narrow 
white bands). In this mine ilmenite occurs in platelike form, distributed 
through the magnetite. Magnifications in all cases 35 diameters. 
148 
