The Missouri Lead and Zinc Deposits. — Jtobertsov. 239 
mainly at Granby, Newton county, and at Aurora, Lawrence 
county. It is in the usual forms and there is little imcom- 
mon in its occurrence. It results from the decomposition of 
blende and coats crystals of that mineral as well as of calcite, 
and frequently forms pseudftmorphs of the latter mineral. 
Smithsonite is likewise found in the usual forms and colors. 
It is the principal ore of zinc found in the southeastern dis- 
trict. In the trade it is known as "silicate"' and is not dis- 
tinguished from calamine. 
Of the lead minerals, galenite is the most abundant and 
important. It occurs in cubes andcube-octohedrons in aggre- 
gates sometimes of large dimensions. In the southeast it is 
found in crystalline and crystallized aggregates associated 
with barite in the tabular and crevice tleposits and in granu- 
lar disseminated form in the magnesian limestones in the 
massive deposits. When deposited on calcite, barite, second- 
ar}'^ chert or other gangue, the crystals are usiuilly well devel- 
oped ; when found in the disseminated deposits the crys- 
tals are generall}^ imperfect. All of the galena of this 
state contains a small quantity of silver, varjnng from 
4^ to 4 ounces per ton. Cerussite is found in all the districts, 
generally near the surface. It is nowhere abundant now, al- 
though it was previously mined in considerable quantities. 
Anglesite and pyromorphite are comparatively rare, and are 
of no commercial importance. 
Calcite is found in a varietj^^ of forms, generally crystallized 
in the usual scalenohedral forms. Sometimes these crystals 
are found with the alternate angles rounded in a very pecul- 
iar way. Barite has been referred to before. It mainl}' occurs 
in the southeastern and central districts; onl}' little is found 
in the southwestern district. It replaces fossils in the Lower 
Carboniferous limestone in Pettis county. Dolomite is abun- 
dant in the southwest but occurs sparingly as a mineral in 
the southeast. It is found in aggregates of snuill crystals, 
sometimes so incoherent as to form a sand. It also occurs in 
curved crystals of the usual shape, of a beautiful peach pink 
color. Pyrite and marcasite are found in all districts although 
the former is rather rare. Marcasite is comparatively com- 
mon in the southwest. (Jhalccqiyrite in small teti-ahedrons is 
also frequently found, (.^uartz in the crystallized state is rare-. 
