PETROGRAPHIC CHARACTER OF OHIO SANDS 155 
pre-Glacial drainage channels. In Gallia County is an ancient, 
abandoned valley which forms a prominent topographic feature 
and has been traced for many miles by Tight,’ who has named it the 
Marietta River. A sand sample taken from a bar deposit in this 
valley has the following mineral make-up: quartz, limonite, 
zircon, tourmaline, apatite, and kaolinite. All of the grains are 
thickly coated with limonite. 
The sands of Group 3, derived by assortment of the Glacial 
drift, are usually of a very heterogeneous nature both as to shape 
of grain and mineral composition. There are sharp, angular 
particles with freshly fractured surfaces that have evidently resulted 
from the crushing and granulation of rock masses. ‘There are also 
well-rounded grains that represent sand deposits in the path of the 
advancing ice front which were carried along and blended with the 
comminuted rock material. During the recession of the ice and 
subsequently, wind and water currents have assorted much of the 
drift into gravels, sands, and silts. In the northern part of the 
state are fine-grained sands and silts that have been deposited in 
the shallow waters of recessional lakes. These sands are remark- 
ably well assorted. Extensive deposits in Erie County are found 
suitable for molding sands. In one sample the diameter of -grain 
was found to range between 0.3 and 0.06 mm. with o.1 mm. as 
an average. Only the largest grains show any rounding. Another 
sample was made up of sharp grains ranging from 0.05 mm. down 
to mineral flour. 
As to mineral content the glacial drift sand is quite distinct from 
the preceding groups. Quartz is still the most abundant mineral, 
but there is almost always a high percentage of accessory minerals. 
Many of these are of a perishable nature and cannot withstand 
solution and decomposition incident to long weathering. Out- 
crops of crystalline metamorphic rocks beyond the Great Lakes may 
be regarded as the source of such minerals. Probably 90 per cent 
of the drift in any one locality is made up of materials derived 
from within fifty miles of that point but there is quite invariably a 
tW. G. Tight, ‘‘ Drainage modifications in southeastern Ohio and adjacent parts 
of West Virginia and Kentucky,” Professional Paper U.S. Geol. Surv. No. 13, p. 76; 
also Plate XI. 
