A PRELIMINARY PAPER ON THE FLORIDA
PHOSPHATE DEPOSITS
E. H. SELLARDS.
THE HARD ROCK PHOSPHATE.-DUNNELLON FORMATION.
The area of hard rock phosphate at present productive, lies in the western part of central peninsular Florida and extends as a narrow strip parallel with the gulf coast in a general north and south direction from southern Suwannee and Columbia Counties to Hernando County, a distance of one hundred miles. Mining has been carried on continuously in this section since 1888. Seventy-four plants under the ownership of twenty mining companies operated in this section during i909. These plants were distributed as follows: Suwannee County, one; Columbia County, three; Alachua County, twenty-two; Marion County, twelve; Citrus County, thirty-four; Hernando County, two. Owing to the depressed condition of the phosphate market a number of these plants closed either temporarily or permanently early in the year while many others closed before the end of the year. At the beginning of I9io, the number of plants in actual operation was thirty-seven. These plants were distributed as follows: Suwannee and Columbia Counties, one plant each; Alachua County, fourteen plants; Marion County, eight plants; Citrus County, twelve plants; Hernando County, one plant. Each phosphate plant operns up in the process of mining one to several pits offering exceptionally good exposures of the phosphate bearing formation. The following notes are based on observations of the exposures made at these and at the many other plants that have operated in this section during the past several years.
LITHOLOGIC DESCRIPTION.
The phosphate-bearing formation as developed in this section includes a mixture of materials from various sources and of the most diverse character, further complicated by pronounced
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