240 The Aiiiericdit Geohxjist. April, 1895 
It has been f>een in the southwest as a coating on galena and 
cerussite and blende. Drusy quartz, or "mineral blossom" is 
quite common in the southeast. There are a number of other 
minerals found in greater or smaller (juantities of little but 
mineralogic interest; such are bitumen, malachite, azurite, 
limonite, goslarite, ferrogoslarite and melanterite. 
The order of deposition of the minerals appears to be the 
following: dolomite, blende, galena, barite, pyrite, calcite. 
This order is not invariable, but is the one most commonly 
found. 
In the southwest the deposits are usually characterized b}^ a 
breeciated structure. This sometimes grades off insensibl}'- 
into the country rock. Some of the crevice deposits in the 
southeast and central districts are breeciated in structure, as 
are also the circle deposits of the latter district. The mas- 
sive deposits of the southeast are, however, characterized by 
a granular or crystalline structure. The dense structure is 
applicable to certain vein deposits in the central and south- 
cast. 
The general form of a southwestern massive ore deposit is a 
series of horizontal runs, which are ore bodies of an ill defined 
oblong shape, and which widen at places into large chambers, 
sometimes several hundred feet in diameter. The galena is 
almost invariably found over the zinc and is frequently in a 
somewhat soft clayey gangue mixed with broken chert, al- 
though it occurs also on chert and limestone. In some mines 
the gangue is composed entirely of original and sec- 
ondary chert, with small amounts of dolomite or dolomitic 
sand, no limestone being visible in the roof, but only found in 
the barren bars. In other mines the gangue is principally 
limestone or dolomite and little or no chert is found. Still 
other deposits, notably those of Webb C'ity, are opened under 
massive roofs of solid, barren limestone of considerable thick- 
ness, under which the ore is found in large chambers, occur- 
ring in the chert breccia and sometimes in Coal Measure shales. 
In the southeastern district, the massive deposits consist of- 
large bodies of the country rock wliich carry, in a more or 
less concentrated state, crystals or grains of galena. Thesie 
rocks contain no chert, although a cherty limestone appears 
to overlie the ore-bearing limestone in some places. In some 
