154 D. DALE CONDIT 
calcite, dolomite, rutile, and apatite. The calcite and dolomite 
occur as minute rhombohedrons which serve as a cementing 
material. The rutile and apatite are needle-like inclusions in the 
quartz. The quartz grains average about 0.3 mm. in diameter 
and are nearly spherical in outline. A chemical analysis shows 
95.11 per cent of silica. 
There is a number of secondary minerals which have found 
place in the old sandstones of Ohio subsequent to their deposition. 
Some of these have resulted from decomposition in place of original 
minerals while others have been brought in from foreign sources 
and precipitated from solution. Some of the secondary minerals 
due to precipitation from solution are: secondary quartz, hematite, 
limonite, calcite, dolomite, siderite, pyrite, and marcasite. Some 
of the alteration products of original minerals are: kaolinite, 
sericite, chlorite, secondary quartz, leucoxene, limonite, and 
hematite. : 
The sands of Group 2, derived by weathering and erosion of 
the old sandstones, are usually loose, uncemented deposits that 
occur as a residuary mantle on the upland or as bar deposits along 
ancient and modern valleys. Such sands may be made up of 
rather angular grains, especially if there was silicification of the 
sandstone whose weathering furnished the material. A coating 
of iron oxide on the grains is quite characteristic. This may be so 
thick as entirely to conceal the interference colors of the quartz 
when viewed under crossed nicols. The minerals of residual sands 
are fewer than those in the original sandstone. Solution and erosion 
incident to weathering eliminate many of the accessory consti- 
tuents and as a result minerals other than quartz and limonite are 
few. Such materials when favorably situated might be reworked 
by wind and water currents to form very pure quartz sand deposits 
comparable with the Sylvania. 
So much of Ohio is covered by glacial drift that most of the 
modern river: sands are a mixture of contributions from local 
sources and from the drift. There are, however, a few counties 
in the southeastern part of the state which have sand deposits 
obtained entirely from local sandstones with no contributions from 
the glacial drift. These deposits ure found along both modern and 
