22 
FLORIDA GEOLOGICAL SURVEY—THIRD ANNUAL REPORT. 
chemical activity within the formation itself. Although exceed¬ 
ingly variable from place to place the prevailing phase of the for¬ 
mation ' is feebly coherent, more or less phosphatic, light gray 
sands. Aside from these sands the principal materials of the for¬ 
mation are clays, phosphate rock, flint boulders, limestone inclu¬ 
sions, pebble conglomerate, erratic and occasional water-worn 
flint pebbles, vertebrate and invertebrate fossils. 
The gray sands may be observed in every pit that has been 
excavated in this section. Moreover, from drill and prospect 
holes it is known that these sands occur very generally over the 
intervening or barren area. The sands are of medium coarse 
texture, the grains being roughly angular. The amount of phos¬ 
phate associated with the sands is variable. They are also more 
or less calcareous in places. Upon prolonged exposure, as seen in 
numerous abandoned pits, these sands oxidize at the surface assum¬ 
ing a pink or purple color. When affected by slow decay and by 
water carrying more or less iron in solution they become reddish 
or ochre-yellow in cplor. 
The clays in this formation occur locally as clay lenses imbed¬ 
ded in the sand, or separating the sand from the phosphate rock, 
or overlying the phosphate rock. The clays are often of a light 
buff, or blue color. When lying near the surface, however, they 
often oxidize to varying shades of red. The relative amount of 
clay in the phosphate-bearing formation increases in a general 
way in passing to the south. The exposures in the southern part 
of the area show as a rule more clay than do similar exposures in 
the northern part of the area. 
Flint boulders occur locally in this formation in some abun¬ 
dance, and occasionally phosphate pits which are otherwise work¬ 
able are abandoned on account of-the number of flint. boulders, 
encountered. The flint boulders are usually oval or somewhat flat¬ 
tened in shape and are of varying size, some weighing several tons. 
The exterior is usually of a light color. Some of the boulders are 
hollow and are occasionally filled with water. Others are solid, 
compact and of a bluish color throughout. Fossils or casts of fos¬ 
sils occur frequently within the boulders. Limestone inclusions 
from the underlying formations are frequent in this formation. 
The pebble conglomerate feature is not of frequent occur¬ 
rence but may occasionally be observed in the northern part of the 
Jiard rock section. Such an exposure of a true pebble con¬ 
glomerate may be seen in one of the pits of plant No. 5 of 
the Cummer Lumber Company about one mile southwest of New¬ 
berry. The matrix at this exposure consists of more or less water 
worn fragments of varying sizes together with round or oval water 
