36 University Geological Survey of Kansas. 
fully in globules in galena of Alston Moor, England; in lava 
of Madeira; in Carthagena, Spain; incarboniferous limestone 
near Bristol and at Kenmare, Ireland; in amygdaloid near 
Weissig; in basaltic tufa in Moravia; in Vera Cruz in lime- 
stone, and in Peru. Recently its occurrence near Saric, 
Sonora, Mexico, has been noted in thin scales and small pel- 
lets. In the United States it is found in limestone near 
Saratoga (?) ; at Breckenridge and Gunnison, Colo.; in the 
Wood River district, Idaho, and in the gold placers of Mon- 
tana. According to Bischof, when found in cavities of vol- 
canic rocks it may have been reduced by high temperatures.’’ 
At Galena a trace of native lead has been found on the sur- 
face of nodules of galena partially dissolved by the ground 
water, and thus given a smooth, rounded surface. 
GALENA OR GALENITE.—A sulphide of lead, PbS. (For 
a detailed description of this and other lead minerals found 
at Galena the reader is referred to descriptions of the same 
given in part III of this volume.) 
Galena is by far the most abundant ore of lead, yielding 
probably much more than nine-tenths of all the lead of com- 
merce. It is a beautiful and very showy mineral, occurring 
generally in modified cubes and octahedra. It cleaves readily 
in three directions at right angles to each other, like the sides 
of a cube, the fresh cleavage faces having a brilliant metallic 
luster, shining almost like a mirror. Often in mining the 
blast scatters myriads of the little shining cleavage particles 
over the walls of the mine, producing a very deceptive ap- 
pearance, leading the unskilled observer to place a greatly 
exaggerated value on the richness of the mine. 
CERUSSITE.—This is a carbonate of lead, PbCO;, and is 
always a secondary mineral produced in one way or another 
by weathering processes acting on galena. Wherever it is 
found, therefore, the rocks and ore bodies have been subjected 
to action of rain waters fresh from the surface still rich in 
oxygen and carbonic acid gas dissolved from the air. Usu- 
ally it is confined close to the surface, but in exceptional 
cases where rain water falls upon open ground, or steeply in- 
clined or broken strata, the weathering processes may be car- 
