THE IRON ORES. 387 
not, carbonaceous matter is never wanting. There is nearly enough of 
this substance generally to calcine the ore. The ore is consequently 
always black, or at least dark in color. Its specific gravity for the same 
reason is light for an iron ore, ranging generally from 2.3 to 2.5. When 
calcined, the figure that represents its gravity is nearly a unit higher 
than the figures above given. The banded structure is very distinct in 
all portions of the ore, as much so as in ordinary bituminous shales. Re 
The raw ore ranges from 20 to 30 per cent. in metallic iron, the 
calcined ore from 45 to 55 per cent. 
Above the blackband proper there are frequently found other large 
accumulations of ore, which by strict classification would need to be 
considered in other divisions, but which can be dealt with to best ad- 
vantage in the present connection. ‘The mountain ore, so-called, is one 
of the forms of limestone ore to which attention has already been 
directed, where carbonate of iron replaces locally the carbonate of lime 
in a stratum of the Freeport type. Many kidneys of ore also occur at 
the same general level. 
The geological place of tne blackband has already been assigned 
(see page 71). It is borne by and is part of the Upper Freeport coal seam. 
It is found only on the outer margin or outcrop of the formation, thus 
far, though notable accumulations of iron can often be found with 
the seam as it descends towards drainage. ‘This marginal development 
of the ore needs to be distinctly recognized. The usual element to 
which we refer in establishing the sections in which the blackland 
occurs is the Middle Kittanning coal, or No. 6 of Tuscarawas county. 
Counting from this, the average interval is about 125 to 130 feet. The 
measured intervals in different portions of the field are as follows: 
110 ft., 114 ft., 117 ft., 118 ft., 120 ft., 120 ft., 125 ft., 130 ft., 132 ft., 
143 ft., 145 ft., 147 ft., 148 ft. and 150 ft. In no single case does the 
measure fall to 100 feet. A difference of 20 feet can often be found for 
the level of the ore itself in different portions of the same basin. The 
ore generally lies on an uneven floor, and frequently in well-defined 
and quite limited basins. 
The first display of blackband as we enter this district from the 
east and north is found in the northeastern corner of Osnaburg town- 
ship (see map on page 65). An area of small extent, perhaps not an 
acre, is found capping a hill with not a dozen feet of cover at the highest 
point. It is owned and worked by the Grafton Iron Company, of Lee- 
