366 
HUBBARD AND CRONEIS 
The Origin of Manganese Ores in Giles County 
The important manganese deposits of Giles County occur in 
clays, sandstones and cherts. Chert, in the Shenandoah, is often 
stained black by the oxide of manganese which in some cases 
is present in sufficient quantity to warrant the name of ore. 
Chert which has been broken into small fragments is often re- 
cemented with manganese oxide or even replaced by it. Both 
the chert and the manganese, being relatively insoluble, have been 
left behind as residual products of the weathering of the lime- 
stone. Some of the deposits are near fault contacts, the con- 
centration being due to the free circulation of ground water in 
the brecciated zone. However, if we except the deposit near 
Bane, described above, prospects in the Shenandoah are small 
and of no great value ; in fact, the only mine of this type which 
has been worked in the county is the one near Newport. It is 
rather interesting to note that, so far as could be ascertained, 
ore of this type occurring in the residual clays of Giles County 
does not show any evident connection with the chert found in 
association. The connection, however, is obvious in the deposits 
of the other counties in southwest Virginia. 
In Giles County by far the largest deposits of manganese 
occur in sandstones of the Giles formation or in the unconform- 
ably underlying Rockwood sandstones. Crests of anticlines seem 
to be the favored position for the accumulation of these deposits, 
due to the fact that these resistant beds, when bent, developed 
fractures wherein ground water could easily circulate. 
Many of the prospects are unique in that they occur on Moun- 
tain tops, such as the Flat Top Mountain prospects. Obviously, 
segregation must have taken place when the present elevation 
of some 3000 feet was part of a peneplain which was not very 
high above sea level. Other deposits occur on benches on the 
flanks of the main ridges. These also were segregated when 
the present elevation was but a part of a smaller, and later 
peneplain than that which was developed in Cretaceous time. 
Of the bench type are the Carrie, Laing, Simpkins, and the 
Spruce Run Mountain prospects mentioned above. 
The association of these ores with particular formations seems 
to indicate that the manganese was deposited in greater quantity 
in certain beds than others, yet only disseminated thinly; and 
that it has been concentrated into its present state, by solution 
