WWR08B.J PHOSPHATES OF FLORIDA. 79 
woru and rounded bones and shells. Prof. 0. U. Shepard, sr., thinks 
that many of the pebbles may be the worn casts of marine shells, while 
some of them seem to be fragments of coral. This conglomerate occurs 
in masses weighing from one to twenty pounds. The largest mass yet 
found was 18 inches long, 14 wide, and 4 thick. The pebbles occur in a 
bed covering about ten acres and are associated with pieces of a porous 
limestone rock, very common in the region. The bed varies from a 
fraction of a foot to five feet in thickuess. Sometimes it crops out at the 
surface, and at others it is found at a depth of four or more feet. At 
Gainesville, a town 19 miles west of this bed, a similar rock is said to 
have been found, in boring an artesian well, at a depth of 248 feet. 
The masses of rock are not nodules, but seem to be simply broken 
fragments. They are much weathered and rounded and are buried in 
sand. 
In some places the pebbles, rounded bones, and coral fragments occur 
loose in a calcareous matrix, as if weathered out of the original con- 
glomerate. Samples of pebbles from this loose material are said by 
one of the owners of this place (Dr. Simmons) to average 85 per cent, 
phosphate of lime, while the whole mass of the rock, as analyzed by 
0. U. Shepard, jr., averages about 48 per cent. 
mm^4Mm--m^m^mi 
girar^jgj ^* — saw 
Fig. 31. Section in quarry at Eocky Hill, on Lochloosa Creek, near Magnesia Springs, Alachua 
County, Fla. A, sandy soil; B, calcareous nodules, white, brown, and purple, embedded in sand; 
C, spongy, calcareous rock, blending at a depth of 3 to 4 feet into a phosphatic rock. Scale : 1 inch= 
8 feet. 
On the northwest side of this bed runs a stream known as Loch- 
loosa Creek, beyond which is a ridge rising sixty to seventy-five feet 
above the creek, and called Rocky Hill. The hill is overlaid almost 
entirely by a deposit of calcareous stones and pebbles, embedded in 
sand, which sometimes entirely runs out, and again reaches a depth of 
over six feet. Below is a soft, porous, calcareous rock, which is of a 
spongy consistency and hardens on exposure to air. It is quarried for 
building the chimneys and foundations of houses. In one of the quar- 
ries examined this formation gradually blended, at a depth of three to 
four feet, into a massive and compact phosphate rock, which is similar 
in appearance to the phosphatic fragments in the bed described above, 
except that it is in a solid mass, and is probably the ledge whence the 
fragments were derived. The surface of the spongy, calcareous rock is 
very uneven and has been much eroded (Fig. 31). It seems as if Eocky 
Hill, when submerged, was much worn before the pebbles and the sand 
were deposited on top of it. 
(553) 
