288 Tlic Auiericaii 6'eo/o///.s7. April, 1S95 
at Galena, Kas.. to whicli districts they are practically con- 
fined. They vary in (jolor from white through all shades of 
drub and brown to l)lack. They exhibit an e(iually wide range 
of texture, varying from a soft shale on the one hand, to a 
rock as hard and considerably tougiier than quartz on the 
other, 'i'hey frequently form tiie matrix of a breccia of angu- 
lar chert fragment*, which they hold with such tenacity that, 
in breaking, the line of fracture will pass through the chert 
fragment without even loosening it. At times the siliceous 
solutions appear to have partially dissolved the original chert 
fragments, thus causing the two to grade into one another. 
This silicification was evidently later than the deposition of 
the ores, as well-formed crystals of the galena and blende are 
frequently found enclosed in this matrix, and on being dis- 
solved out leave perfect exterior casts. Secondary limestones 
occur in some deposits, but, so far as noticed, df) not appear to 
be common. In specimens of such, the limestone forms the ma- 
trix of the chert breccia and often encloses crystals of blende. 
Dolomite, other than the magnesian limestones of the Ozark 
stage and ;)f the pink crystals which are merely of mineralogi- 
cal interest, is principally found in the southwestern district. 
It is usiudly composed of a dense though incoherent mass of 
gray, grayish white or drab dolomite crystals. It appears to 
have been formed by magnesian solutions acting on the lime- 
stones into which it often grades. Barite occurs as a gangue 
mineral in the southeastern and central districts. It is gen- 
erally of the opaque white variety, tinged with iron on ex- 
posed surfaces. Vuggs occur in it lined with tabular crys- 
tals. It also occurs in sonu> localities in limited (luantities in 
large tabular, scmi-ti'ansparent crystals, colorless or of a l)lu- 
ish tint. 
The minerals include the zinc aiid lead conipountis and the 
accessory minerals. 
The zinc minerals are sphalerite, calamine, smithsonite and, 
rarely, hydrozincite. Sphalerite is found crystallized through- 
out the ore body and encrusting cavities. It is seen deposited 
on chert, limestone and dolomite. It is generally of a dark 
red color with a resinous luster, but is also found of a bright 
yellow color and often in small crystals of cinnanu)n and gar- 
net colors. Calamine, locally known as '"silicate," is fouiul 
