65 
CARBON niNERALS. 
The minerals of which carbon is the chief or only constituent, 
afford a vast variety of products useful to man. 
In the group are included the diamond, hard, transparent, 
lustrous and graphite, soft, black and dull; with them the great 
variety of mineral coals, petroleum, bitumens, asphaltum, etc. 
They furnish gems, fuels, sources of illumination, dyes, medicines, 
lubricants, paving and roofing materials, etc. A knowledge, there- 
fore, of their characteristics and modes of occurrence in nature, is 
of great importance. They are illustrated by the collections in 
Halls 69, 70 and 71. 
HALL 69. 
Here one may study the distribution and extent of the coal 
fields of the United States, also the kinds of coal produced by 
each and the available means of transportation. 
On a large plate-glass map in the center of the hall, scale ten 
miles to one inch, the coal fields of the United States as at present 
developed are indicated by areas in black, and the principal rail- 
roads connecting them are also represented. 
Cases 1-18 contain specimens taken from these different 
fields, the exact locality of each being shown by red figures on the 
labels corresponding to those on the map. The order of numbers 
is the same as the alphabetical order of the States. The specimen 
labels show the uses of the coal, the name of the operators of the 
mine, the means of transportation and the markets. Analyses 
have: been made of all the specimens and this data will be given 
to any one desiring to obtain it, on application to the Curator* 
