THE NONMETALLIC MINERALS. 427 



Connellsville Basin of Pennsylvania, and (II) a cannel coal froiu Ka- 

 nawha Countj 7 , West Virginia. 1 



ANTHRACITE COAL. This is a deep black, lustrous, hard and brittle 

 variety, and represents the most highly metamorphosed variety of the 

 coal series. Traces of organic nature are almost entirely lacking in 

 the matter of the anthracite itself, though impressions of ferns, lyco- 

 pods, sigillaria and other coal-forming plants are frequently associated 

 with the beds in such a manner as to leave little doubt as to their 

 origin. Anthracite is ignited with difficulty and burns with little 

 flame, but makes a hot fire. Below is given the average composition 

 of a coal from the Kohinoor Colliery, Shenandoah, Pennsylvania. 8 



Water 3. 163 



Volatile matter 3. 717 



Fixed carbon 81. 143 



Sulphur 0. 899 



Ash . 11.078 



100. 00 



(Specimens Nos. 59058, 59062, from Pennsylvania, and 30854, from 

 Colorado, are sufficiently characteristic.) Like the other coals, anthra- 

 cite occurs in true beds, but is confined mostly to rocks of the Car- 

 boniferous age. Thin seams of anthracite sometimes occur in Devo- 

 nian and Silurian rocks, but which are too small to be of economic 

 value. Rarely coals of more recent geological horizon have been 

 formed locally, altered into anthracite hy the heat of igneous rocks. 

 Through a still further metamorphism, whereby it loses all its volatile 

 constituents, coal passes over into graphite (Specimens Nos. 17299 

 and 59099, from near Newport, Rhode Island), and it is possible, though 

 scarcely probable, that all graphite may^ have originated in this way. 

 The principal anthracite coal regions of the United States are in 

 eastern Pennsylvania. From here westward throughout the interior 

 States to the front range of the Rocky Mountains the coals are all 

 soft, bituminous coals. Those of the Rocky Mountain region proper 

 are largely lignitic, passing into the bituminous varieties. 



1 F. P. Dewey, Bulletin 42, United States National Museum, 1891, p. 231. 

 1 Idem, p. 221. 



