PUERTO RICO, PANAMA, VIRGIN ISLANDS, PACIFIC ISLANDSTable 3.—Portland
cement production and shipments 
697 
 
Year 
Production 
(376-pound 
barrels) 
 
Shipments 
 
 
 
— 376-pound 
barrels 
Value 
 
Average per 
Thousands barrel 
 
1963                                   
1964                                   
7,171,302 
7,910,624 
7,217,417 
7,925,781 
$22,090 
23,879 
$3.06 
3.01 
1965                                   
7,268,773 
7,284,219 
23,415 
3.21 
1966                                   
1967                                   
8,071,343 
7,963,096 
7,602,641 
8,446,616 
24,277 
27,397 
3.19 
3.24 
 
 The Puerto Rican Cement Co. installed a new dust control system at its Ponce
plant in a continuing effort to reduce air pollution. Electrostatic precipitators
designed to eliminate 98 percent of the dust were installed in the smokestacks.

 Clay.—---Most of the clay production was used in making cement. Sandy
clay, used for fill on various construction projects, was not included as
mineral production. The value of land in Puerto Rico permits usage of pit-run
fill selling for as much as $1 per cubic meter. 
 Diazlite, Inc. operated its lightweight aggregate plant near Trujillo Alto,
and Puerto Rico Ceramics Corp. mined clay near Caguas for making holk~w structural
tile. 
 Lime.—Puerto Rican Cement Co., Inc., processed limestone into quicklime
and hydrated lime at Ponce. Most of the hydrated lime was used as mason's
lime in 
construction work. Other uses for the quicklime and hydrated lime were for
steel (electric furnaces), soil conditioning, sugar refining, leather tanning,
and water purification and softening. 
 Salt.—Evaporated salt was recovered from ponds and processed by Ponce
Salt Industries, Carlos Ramirez, and other producers along the southwest
coast. Users of the salt included nearby chemical plants and seafood processors
and canners. 
 Sand and Gravel—The gain in construction activities accounted for
a corresponding increase in concrete aggregates. The greatest increases were
in highway construction and industrial facilities such as petrochemical plants.
Silica sand from inland beds west of San Juan was used in the nearby cement
and glass plants, in foundries, in sandblasting, and in marble polishing.
Puerto Rico Glass Corp. used white, high-grade silica sand in making bottles
and jars.