PETROGRAPHIC CHARACTER OF OHIO SANDS 153 
obtained from the drift by the action of wind and water currents. 
Each group has certain physical and mineralogical features which 
are quite characteristic of the sand wherever found and which will 
be described. 
The old sandstones of Group 1 are made up of travel-rounded 
grains cemented more or less firmly by silica, limonite, hematite, or 
some other bond. Quartz is by far the most abundant mineral. 
The accessory constituents seldom make as much as 15 per cent 
of the sand. They are minerals of a rather stable nature together 
with secondary products derived from the decompositon of the 
less stable original minerals. Orthoclase and plagioclase are as a 
rule much decomposed and their presence is shown by aggregates 
of sericite, kaolinite, and secondary quartz. Occasionally plagio- 
clase grains are seen which still show twinning lines. Microcline 
is almost invariably fresh and unaltered. Tourmaline is common. 
Muscovite is widely distributed, being found in nearly every sand, 
but biotite is rare. Amphibole and pyroxene are almost entirely 
altered to chlorite, limonite, and other secondary products. No 
garnet was found in any of the sandstone samples. A sand from 
the Sharon Conglomerate of Summit County is regarded as repre- 
sentative of the group and its mineral list follows. The minerals 
are listed in order of abundance. 
1. Quartz 8. Plagioclase 
2. Muscovite g. Sericite 
3. Kaolinite 10. Hematite 
4. Microcline 11. Apatite 
5. Zircon 12. Chlorite 
6. Limonite 13. Rutile 
7. Orthoclase 
There is a slight bond of sericitic kaolinite and limonite. Some 
of the quartz grains show slight secondary growth. The feldspars 
are almost entirely altered and their outline is preserved by aggre- 
gates of sericite, kaolinite, and secondary quartz which are so 
interlocked as to resemble a mosaic pattern. 
The Sylvania (Silurian) formation of northwestern Ohio is a 
good illustration of a very pure sand having few accessory minerals. 
A sample from Lucas County was found to contain only quartz, 
