RoGERs. | Minerals of the Galena-Joplin District. 503 
PARAGENESIS OF THE MINERALS. 
_ Paragenesis, or order of formation of minerals, is a very 
interesting subject. It is especially valuable to the geologist 
and to the student of ore deposits, as it is a prime factor to 
be considered in working out a theory as to the deposition of 
ore in any given locality. 
The order in which the minerals of the Joplin district were 
formed is not an invariable one, yet there is a general order 
which it is believed will hold in the majority of cases. The 
order of deposition of the original minerals (secondary min- 
erals being formed at any time subsequent to the original 
ones) is as follows: Dolomite, galena, sphalerite, chalco- 
pyrite, marcasite, pyrite, calcite, barite. 
In order that the reader may judge for himself, some of the 
data upon which this conclusion is based are given below. 
Many of the specimens which furnish these data are in the 
display collections at Joplin. 
Dolomite, sphalerite, calcite. 
Dolomite, galena, sphalerite, chalcopyrite. 
Dolomite, galena, chalcopyrite. 
Dolomite, galena, sphalerite, calcite, barite. 
Dolomite, sphalerite, chalcopyrite, marcasite, calcite, barite. 
Sphalerite, chalcopyrite, barite, calcite. 
Dolomite, galena, sphalerite, chalcopyrite, marcasite, calcite. 
Dolomite, galena, sphalerite, chalcopyrite, marcasite, barite. 
Galena, sphalerite, pyrite. 
Galena, pyrite, calcite. 
Dolomite, galena, sphalerite, chalcopyrite, marcasite, pyrite. 
Galena, sphalerite, marcasite, pyrite. 
Galena, sphalerite. 
Galena, sphalerite, dolomite. 
Galena, dolomite. 
Sphalerite, chalcopyrite, pyrite. 
Chalcopyrite, marcasite. 
Pyrite, sphalerite (small, reddish crystals in cavity ). 
Sphalerite, dolomite, calcite, barite. 
Dolomite, calcite. 
Sphalerite, galena (small, octahedral crystals). 
Sphalerite, chalcopyrite, galena (small cuts, octahedrons). 
Sphalerite, galena (cuts, octahedrons). 
Dolomite, chalcopyrite, calcite. 
Dolomite, galena and sphalerite belong to the first period 
