450 University Geological Survey of Kansas. 
ing as the native element. The localities for this mineral 
are the Bonanza grounds, northwest of Galena, and Crowe & 
Ping’s crusher, on the South Side grounds, Galena. 
Sulphur was also observed in cavities in sphalerite in small 
quantities. The sphalerite often occurs as crystals in sec- 
ondary chert, or cherokite, as it has been called by Jenney. 
The crystals show various stages of decomposition, from the 
unaltered mineral to the highly corroded fragmentary rem- 
nant remaining in the cavity. In some cases the cavity 
alone remains and occasionally is occupied by crystals of an- 
olesite. 
Galena; ‘‘LEAD,’’ ‘‘ MINERAL.’’ 
Composition, lead sulphide, PbS; lead=86-6%; sulphur=13-3%; hard- 
ness, 2-5—2-75; gravity, 7-43; color, lead gray; crystallization, regular sys- 
tem; cleavage, highly perfect, parallel to cube faces. 
Observed forms: c{100} oO; p,j111}O. 
The mineral galena occurs crystallized in cubes, often with 
the faces of the octahedron acuminating its solid angles, as 
in figure 1. Rarely the octahedron face is the dominant 
form, and sometimes it alone is present. Some crystals from 
the J. J. Luck mine No. 1, occurring in a clayey matrix, are 
flattened parallel to one of the octahedral faces, and are con- 
sequently pseudo-rhombohedral in appearance. 
Evidences of twinning are apparent in many of the crys- 
tals and cleavage pieces, though only in a comparatively few 
cases can definite twins be observed. Such cleavage faces 
present a number of parallel bands, alternate ones of which 
reflect light simultaneously. These are twinning lamelle, 
and resemble those so common in the triclinic feldspars. On 
one of the cube faces the bands are parallel to the diagonal of 
the cube. Tracing them over to the other faces of the cleav- 
age cube they are seen to be approximately parallel to the 
cleavage line. Thus the twinning plane is a trigonal tris- 
octahedron. ‘To determine the symbol of this form which 
serves as twinning plane the angle which the traces of the 
bands make on the cube faces was measured. Results of 
these measurements are given here, the letters referring to 
figure 2: a,b—5° 25’; bpc=3° 30’; cp~d==4° 30’. Several 
