106 FLORIDA GEOLOGICAL SURVEY- 15 TH ANNUAL REPORT 
Slip-Clays —A slip-clay is one used as a natural glaze. It should be 
of fine, even texture, have a high percentage of fluxing impurities, and 
should melt to a greenish or brown glass at a low cone. 
Miscellaneous —Clays used when burned, not included in the above 
mentioned groups, are: Gumbo-clay, having a high shrinkage, dense 
character, and fine grain, is used extensively as railroad ballast. Sagger- 
clay is used in making the saggers or boxes in which white ware and 
other high grades of pottery are burned to protect them from the flame 
and fuel gases. Their refractoriness must be above that of the product 
burned. Wad-clay is a low grade of fire clay used for sealing the joints 
between saggers when they are set in the kilns. Portland cement clay is 
that used in the artificial mixture of silica, alumina and lime which com¬ 
poses Portland cement. Clay or shale usually supplies the silica and 
alumina and limestone or marl the lime. The adaptibility of a clay for 
Portland cement can only be determined from a chemical analysis. 
Many clays are used in the unburned condition as paper fillers, paint 
pigments, abrasives, etc. 
USES OE CLAY 
The uses of clay are many and varied and any attempt to list all of 
them would be hopeless. The following uses listed by Ries 1 summarizes 
those of raw clay as well as those of the fire or burned clay: 
Domestic —Porcelain, white ware, stoneware, yellow ware, Rockingham ware 
for cooking and for table service, majolica stoves, polishing brick, bath brick, fire- 
kindlers. 
Structural —Brick, common, front, pressed, ornamental, hollow, glazed, adobe, 
terra-cotta, roofing tile, glazed and encaustic tile, drain tile, paving brick, chimney 
flues, chimney pots, door knobs, fireproofing, terra-cotta lumber, copings, fence posts. 
Refractories —Crucibles and other assaying apparatus, gas retorts, fire-brick, 
glass pots, blocks for tank furnaces, saggers, stove and furnace bricks, blocks for fire 
boxes, tuyeres, cupola molds, mold linings for steel castings. 
Engineering —Puddle, Portland cement, railroad ballast, water conduits, tur¬ 
bine wheels, electrical conduits, road metal. 
Hygienic —Urinals, closet bowls, sinks, washtubs, bathtubs, pitchers, sewer pipe, 
ventilating flues, foundation blocks, vitrified bricks. 
Decorative —Ornamental pottery, terra-cotta, majolica, garden stands, tomb¬ 
stones. 
Minor Uses —Food adulterant, paint fillers, paper filling, electric insulators, 
pumps, fulling cloth, scouring soap, packing for horses’ feet, chemical apparatus, 
condensing worms, ink bottles, ultramarine manufacture, emery wheels, playing 
marbles, battery cups, pins, stilts, and spurs for potters’ use, shuttle eyes and thread 
guides, smoking pipes, umbrella stands, pedestals, filter tubes, caster wheels, pump 
wheels, electric porcelain, food rules, plaster, alum. 
1 Ries, H., Clays, Their Occurrence, Properties and Uses, p. 252, 1908. 
To this list of clay products should be added turpentine cups, which are very 
extensively used in Florida. R. M. H. 
