902 GEOLOGY OF OHIO. 
is well developed at several points in Green township, Hocking county, 
and especially on Kitchen Run. In the vicinity of Junction City, 
many thousands of tons have been raised. It is also found in Vinton 
county, but has not been noticed south of the Marietta and Cincinnati 
road. Its position is easily remembered on account of its relation to 
the Blue or Zoar Limestone, the main seam of which it underlies by 
fifteen feet, and the lower seam of which it covers when the latter is 
present. It yields forty per cent. of iron and isin every respect a valua- 
ble element of our geological scale. 
5. The next ore in ascending order is one of the most widely dis- 
tributed and important of our whole series. It is the block ore which 
immediately covers the main Zoar Limestone, and is designated in the 
section as the Main Block. Situated thus in the most conspicuous horizon | 
of our Lower Coal Measures, it is universally known and through con- 
siderable districts is styled the block ore, although it is never the only 
seam of this class. Under cover, it is often a close-grained, heavy blue 
carbonate, but along its outcrop, it is everywhere an easily worked and 
excellent limonite. It agrees in general character with the ore last 
dsscribed, like it yielding forty per cent. and over, of iron in the furnace. 
Is seldom exceeds a foot in thicknes and eight inches will make a very 
satisfactory average wherever it is worked. Though ore isalways shown 
at this horizon, it is by no means to be concluded that the ore is always 
valuable. There are very many areas in which it is too thin or too sili- 
cious to have any value. It shows its marine origin in some instances 
by containing fossil shells. Such a phase of it is seen at the old Hocking 
Furnace, at Haydenville. It shares this peculiarity with the seam next 
to be named. | 
It is co-extensive with the limits of the limestone but it does not disap- 
pear with that formation. The limestone is lost in Scioto county, a few 
miles north of the Ohio River, but the ore retains its place with perfect 
ila 
rood 
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iwwity and furnishes the means of identifying the various elements 
of the scale that are associated with it. Itis the lowest of three block 
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ores that are extensively worked among the southern furnaces, and when 
all three are worked on the same lands, this ore is generally known as 
the “little block ” or “little red block.” It must, however, be confessed 
that the same terms are sometimes applied to the other ores of the 
series. 
6. Following the Upper Main Block Ore at an interval of twenty-five 
to forty feet, quite a persistent seam occurs, the most common designa- 
tion of which is the Rough Block Ore. It is also called the Sand-block, 
but neither name is distinctive. It has been worked to a small extent 
