158 FLORIDA GEOLOGICAL SURVEY I3TH ANNUAL REPORT 



hard rock and about half the land pebble is exported to Europe in 

 normal times.* 



Since the war the biKiness has picked up again, and several new 

 mines have been opened in the flatwoods or pebble district, and more 

 attention is being paid to the soft phosphate formerly wasted in the 

 hard rock district. Another by-product, chiefly from the pebble 

 district, is a sandy rock containing too little phosphorus for ferti- 

 lizing purposes, but making a pretty good road-surfacing material. j 



Limestone is probably next in importance to phosphate in our 

 area. It has long been quarried in several places around Ocala, and 

 recently in southeastern Citrus County. Some of it is burned for 

 lime and some used for road material, and in a few places it has been 

 sawfed into blocks and used for chimneys, walls, etc. A variety 

 known as coquina, composed of shell fragments rather looseiy ce- 

 mented together, occurs in a few places along the east coast, and 

 has been used locally for building purposes. 



Bog iron ore is said to have been mined and smelted near Levy- 

 ville in Levy County during the Civil War, for the Confederate 

 government. 



Deposits of kaolin or porcelain clay are being worked on the 

 south side of Lake Harris in Lake County, and brick is made at 

 Whitney in the same county, and formerly at Brooksville and a few 

 other places. Sandy clay suitable for road surfacing is widely dis- 

 tributed, particularly in the lake region. 



*The exportation of so much valuable fertilizing material has been viewed 

 with alarm, by some writers, but it is a natural result of the normal working 

 of the- law of supply and demand. Substantially the same arguments might 

 be used against shipping coal, iron or lumber from states that have them to 

 those that lack them ; but if other states or countries need these things and 

 have something of greater present value to us to offer in exchange iti is per- 

 fectly good business to make the trade. It seems to be generally true of min- 

 eral fertilizers that the soiils near where they occur are pretty well supplied 

 with that particular substance, so that they have to be transported a consild- 

 erable distance to do the utmost good. By sending our phosphate to Germany, 

 •Nebraska or California in exchange for potash both sides are benefited, pro- 

 vided the cost of transportation, etc., is not too great. 



tFor a discussion of the Florida phosphates see papers by Dr. E. H. Sellards 

 in our Fifth and Seventh Annual Reports, and U.. S. Geological Survey Bul- 

 letin 604, by G. C. Matson (1915). The first and last of these contain many 

 references to earlier papers, which need not be cited here. 



