158 D. DALE CONDIT 
cent of quartz. The most impure sandstone inspected had about 75 per cent. 
The purest sand on analysis showed a little more than 08 per cent of quartz. 
Quartz is also the principal mineral in sands selected for molding purposes 
but in some cases it is slightly less than the sum of all the accessory minerals. 
In glacial drift sands it usually ranges from 50 to 70 per cent. It may consti- 
tute as much as go per cent of residual sands derived from weathering of the 
sandstones. 
Feldspars.—Feldspars probably rank next to quartz in abundance and 
distribution. About three-fourths of the sandstone samples have feldspar. 
Plagioclase was recognized in one-fourth of the rock samples and orthoclase 
in one-fifth. Both are almost invariably much decomposed and in many cases 
can only be called ‘‘much-altered feldspar” without closer identification. 
Microcline is present in more than one-half of the samples and is one of the 
principal accessory minerals. It shows little decomposition even in the oldest 
sandstones. In the most arkosic sandstones of Ohio the feldspar content is 
usually less than ro per cent. 
The glacial drift sands have a large percentage of feldspar. This may 
be as much as 25 per cent in some cases. Orthoclase and plagioclase showing 
little or no decomposition are common. ‘These minerals are entirely wanting 
in the residual sands but microcline is occasionally found. 
Amphibole—Hornblende and actinolite, the common varieties of amphi- 
bole, are almost entirely limited to the recent sands. Nearly every glacial 
drift sand contains actinolite and a lesser amount of hornblende. A few of the 
sandstones have much decomposed remnants of what appears to be actinolite. 
That these minerals were formerly present in many of the sandstones is shown 
by chlorite and other alteration products. 
Pyroxene.—The common varieties of pyroxene in sands are diopside, 
enstatite, and hypersthene. Augite is less common. All are limited to recent 
sands of glacial drift origin. No pyroxene was seen in the sandstones but its 
former presence is indicated by alteration products. 
Mica.—Muscovite flakes visible without a microscope are present in about 
two-thirds of the sandstone samples and one-half of the uncemented sands. 
Sericite is a common product from the alteration of feldspars. Biotite is rare 
even in the glacial drift sands. 
Tourmaline-—This is very widely distributed. It was found in nearly 
three-fourths of the samples examined. 
Zircon.—Zircon is nearly always present. It was found in over four-fifths 
of the samples. 
A patite—About one-half of the samples were found to contain apatite. 
Both inclusions and free grains are common. 
Rutile—Nearly every sand has a small amount of rutile. Microscopic 
hairlike inclusions in quartz and free grains are the modes of occurrence. 
Garnet.—Garnet is one of the principal accessory minerals of glacial drift 
sands. It was not found in any of the sandstones or residual sands. 
