Rogers. | Minerals of the Galena-Joplin District. 491 
The pink color of the dolomite is evidently due to a small 
amount of ferrous carbonate, for specimens which have been 
exposed to the atmosphere for a long period of time are almost 
invariably stained a lighter or darker brown color. 
Pseudomorphs of smithsonite and calamine after dolomite 
are of frequent occurrence, especially at Granby. 
Dolomite is one of the earlest minerals to be formed. Itis 
contemporary in origin with sphalerite and galena. 
Smithsonite ; ‘‘CARBONATE.’”’ 
Composition, zinc carbonate, ZnCOs: Zn, 51-78%; C, 9-50%; O, 38-40%. 
Hardness, 5; gravity, 4-3-4-5; color, white, often grayish, greenish, brown- 
ish; crystallization, rhombohedral; cleavage, rhombohedral. 
Observed forms: p-(1011)+R; ¢-(0221)—2R. 
The only well-defined crystals observed were small ones 
with these two forms. The crystals are almost invariably 
rough and much curved. Two general varieties may be dis- 
tinguished: the one, long crystals with steep rhombohedral 
faces terminated by those of a low rhombohedron; the other, 
short crystals with the faces of a low rhombohedron. Bot. 
ryoidal, mammillary and stalactitic forms are common, often 
lining cavernous interiors. 
Pseudomorphs after calcite and dolomite are frequently 
found at Granby, the calcite crystals, when their forms can 
be recognized, being those of type 18. At Granby are found 
‘masses of smithsonite, pseudomorphous after calcite, only 
the cleavage cracks of the latter giving a clue to former ex- 
istence of the calcite. Figures of such pseudomorphs are 
given on plate XXII, vol. VII, of the Missouri Geological 
Survey. Large calcite crystals coated with calamine have 
been replaced by smithsonite, the calcite completely, the 
calamine only partially, some of the unaltered mineral re- 
maining unchanged. 
In color, smithsonite ranges from white to black; gray, 
yellow, bluish and brownish colors being very common. The 
prominent localities are Granby and Aurora. In Kansas 
smithsonite is found in several mines in Empire City, while 
it also occurs at a mine south of Galena. 
