RoaeErs. | Minerals of the Galena-Joplin District. 467 
the western part of Galena, and from the mines east of Au- 
rora is probably pyrolusite. It has a botryoidal surface and 
the streak is black with submetallic luster. It reacts for 
manganese and in the closed tube gives off a small amount 
of water, as pyrolusite often does. Dendritic markings of a 
black color on chert at Granby may probably be referred to 
this mineral. 
Limonite. 
Composition, 2F'e203-3H:0; iron, 59:8%, water, 15:-5%; hardness, 5-5-5; 
gravity, 3-6-4; color, various shades of brown; crystallization, not crystal- 
lized. - 
Limonite is very commonly observed as a thin coating or 
stain of yellow or brown color on the rocks. 
Pseudomorphs of limonite after pyrite, marcasite and chal- 
copyrite are not uncommon. 
Calcite; ‘‘Tirr.’’ 
Composition, calcium carbonate, CaCOs; calcium, 40%; oxygen, 48%; 
carbon, 12%; hardness, 3; gravity, 2-713; color, white or colorless, also va- 
rious shades of gray, pink, blue, violet, yellow, and brown, due to impuri- 
ties; crystallization, rhombohedral; cleavage, rhombohedral. Observed 
forms, see table I. 
IntRopucTION.—The only crystallographic study of the 
calcites of the district has been that made by Farrington,” 
who distinguishes five types of crystals and gives thirteen 
crystal forms." Farrington’s material comprises the more 
typical of the larger crystals occurring in the immediate vi- 
cinity of Joplin, but is rather limited when the whole dis- 
trict is taken into consideration. 
The material at the disposal of the writer was exceptionally 
complete, amounting in all to perhaps as many as 1000 crys- 
tals. They were, for the most part, collected by him during 
the summers of 1899 and 1900 in all parts of the district. 
Besides this a number of specimens in the University of Kan- 
sas Museum, collected in previous years, was at hand. A 
suite of 137 crystals, principally of types 1, 2, and 4, was 
10. Publications of the Field Columbian Museum, Geological Series, vol. I, No. 7, pp. 282-241, 
11. Since the above was written, the writer has come across a reference to the Joplin cal- 
cites in the Bull. Soc. Francaise de Mineralogie, vol. 20, pp. 110, 111, 1897. Pisani, in presenting 
two calcite crystals from J oplin to the society, notes the crystal forms present as —3R, R, 
+R§+ R38, +4 R5, +$R$ and 3 P2, of which the three latter forms were not observed by either 
Farrington or the writer. But as no measurements are given they are not included in the list. 
