162 RE-EXAMINATION OF AMERICAN MINERALS. 



sometimes it lines cavities in the rock that are completely filled 



with cubical galena. Acicular concretions of the hematite are 



found traversing crystals of anglesite and cerusite. A specimen 



of the purest hematite gave for its composition 



Peroxide of iron 80.32 



Oxide of copper 94 



Oxide of lead 1.51 



Water 14.02 



Silica 3.42 



100.21 

 62. Fluor-spar. 



The remarkable feature of the fluor-spar of this mine is the 

 absence of color, all the specimens yet found being colorless and 

 transparent. The crystals are very perfect and beautiful, yet 

 small; it is sometimes in globular concretions of crystalline 

 structure radiating from the center. The cube, which is the 

 more common crystalline form, is sometimes very much modi- 

 fied by the truncation of the edges and angles. A specimen 

 that was examined gave a specific gravity of 3.15 and the 

 following composition : 



Fluorine 48.29 



Calcium. 50.81 



Phosphate of lime trace 



99.10 

 It is associated with calc-spar, and in some instances in a 

 remarkable manner, mentioned under the head of calc-spar. 

 Galena and blende are interspersed through it. Its occurrence 

 in the mine was first noticed at the depth of three hundred 

 feet, and since then it has been found abundantly. 



63. Calc-spar. 



There are a variety of interesting forms and associations 

 of this mineral. The two most common are the dog-tooth 

 spar and the hexagonal prism with a three-sided summit, and 

 occasionally the hexagonal prism with flattened summits like 

 aragonite. Sometimes slabs of this mineral are found, with a 

 surface of eight or ten square feet completely covered with 

 prismatic crystals an inch or two in length, and from half an 

 inch to an inch in thickness ; they are mostly vertical, but 

 occasionally horizontal with double terminations. These crys- 



