The geology of the Florida land-pebble phosphate deposits

Trace Elements Investigations 265
This report concerns work done on behalf of the Division of Raw Materials of the U.S. Atomic Energy Commission
By: , and 



The land-pebble phosphate district is on the Gulf Coastal Plain of Florida. The phosphate deposits are in the Bone Valley formation, dated Pliocene by most writers. These strata overlie the Miocene Hawthorn formation and are overlain by consolidated sands 3 to 20 feet thick.

The minable phosphate deposits, called “matrix” in the district, range from a featheredge to about 50 feet in thickness and consist of phosphatic pellets and nodules, quartz sand, and montmorillonitic clay in about equal proportions. Locally the matrix displays cross-bedding and horizontal laminations, but elsewhere it is structureless. The phosphorite particles, composed largely of carbonate-fluorapatite, range in diameter from less than 0.1 mm to about 60 cm and in P2O5 content from 30 to 36 percent. Coarse-pebble deposits, containing 30 to 34 percent P2O5 are found mainly on basement highs; and fine-pebble deposits, containing 32 to 36 percent P2O5 are, are found in basement lows. Deposits in the northern part of the field contain more phosphate particles and their P2O5 content is higher than those in the southern part.

The upper part of the phosphatic strata is leached to an advanced degree and consists of quartz sand and clay-sized particules of pseudowavellite and wavellite. The leached zone ranges in thickness from a featheredge to 60 feet.

The origin of the land-pebble deposits is incompletely known. Possible modes of origin are a residuum of Miocene age, or a reworked residuum of Pliocene or Quaternary age.

Study Area

Publication type Report
Publication Subtype USGS Numbered Series
Title The geology of the Florida land-pebble phosphate deposits
Series title Trace Elements Investigations
Series number 265
DOI 10.3133/tei265
Year Published 1952
Language English
Publisher U.S. Geological Survey
Description 21 p.
Country United States
State Florida
Other Geospatial Gulf Coastal Plain
Google Analytic Metrics Metrics page
Additional publication details