212 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. [bull. 213. 
under similar conditions, and both are found replacing sandstone to 
a greater or less extent. 
The usual mode of occurrence of fluorite is massive and granular. 
It is also found as cubic crystals in vugs or coating the walls of small 
fractures in the country rock; but well-crystallized occurrences are 
comparatively rare. It is generally translucent, though rarely trans- 
parent; its color is usually white, sometimes purple, and occasionally 
yellow. 
Calcite and barite, — Of the minerals associated with the fluorite 
calcite is the most abundant, It occurs as white crystals or coarsely 
granular masses scattered through the veins. Barite is next in 
amount, though it is not found in most of the veins. AVhere it occurs 
with the fluorite it is apparently intergrown with it. There are also 
in both the St. Louis and the Princeton limestones veins of fine-grained 
barite occurring either alone or with a minor proportion of fluorite; 
but so far, except in one instance, this mineral has not been found in 
sufficient quantity to pay for mining. 
Galena, — Galena occurs in many of the fluorite veins, sometimes in 
quantities large enough to make it profitable as a by-product, though 
in most cases it is insignificant in amount. It usually occurs in grains 
and crystals of varying size, though generally small, disseminated in 
the fluorite, for the most part near the Avails of the veins, and fre- 
quently concentrated in lines parallel to the walls. Occasionally 
it is met in elongated columnar forms, due to shearing in the veins. 
Sphalerite. — Fragments of the wall rock, whether quartzite or lime- 
stone, are common in most of the veins. They have in some cases 
been replaced by fluorite to a greater or less extent. Sphalerite, 
which is found in many of the veins, occurs mainly as minute grains 
disseminated in the included fragments of limestone, frequently con- 
centrated near the contact between the fragments and the inclosing 
fluorite. It is also found occasionally disseminated in the fluorite 
and in the wall rock where this is of limestone. This fine-grained 
sphalerite is more abundant, on the whole, than the galena, and will 
prove of economic importance if a satisfactory method of separating 
it from the associated fluorite is found. Sphalerite is also found here 
and there (especially in the region southwest of Crittenden Springs) 
in coarser form and in greater amount. 
There are a number of deposits in which sphalerite or its oxidation 
products have been found apparently unassociated witli fluorite, 
notably in the Old Jim mine, where the ore (smithsonite with some 
hydrozincite) occurs adjacent to a dike of peridotite. Here as in other 
similar instances, however, mining has not been carried deep enough 
to show the character of the unoxidized ores. 
Effects of oxidation. — Above ground-water level the oxidized and 
carbonated surface waters have removed from the veins much or 
most of the calcite which they contained, as well as the included 
fragments of limestone, and have altered the country rock to a greater 
