Geologic Features
Fuller's earth is essentially a variety of clay having a high absorptive power which makes it useful for decolorizing and purifying purposes. Fuller's earths are in general higher in water content and have less plasticity than most clays, but they vary widely in physical and chemical properties. Chemical analyses are of little value in determining whether a given clay will serve as fuller's earth, and an actual test is the only trustworthy criterion.
Deposits of fuller's earth may occur under the same variety of conditions as deposits of other clays. The deposits of Florida and Georgia consist of beds in slightly consolidated flat-lying Tertiary sediments, which are worked by open cuts. The Arkansas deposits are residual clays derived from the weathering of basic igneous rocks, and are worked through shafts.
GRAPHITE (PLUMBAGO)
Economic Features
Crystalline graphite is used principally in the manufacture of crucibles for the melting of brass, bronze, crucible steel, and aluminum. About 45 per cent of the quantity and 70 per cent of the value of all the graphite consumed in the United States is employed in this manner. Both crystalline and amorphous graphite are used in lubricants, pencils, foundry facings, boiler mixtures, stove-polishes and paint, electrodes, and fillers or adulterants for fertilizers. The most important use of amorphous graphite is for foundry facings, this application accounting for about 25 per cent of the total United States consumption of graphite of all kinds. Artificial graphite is not suitable for crucibles or pencils but is adapted to meet other uses to which natural graphite is put. It is particularly adapted to the manufacture of electrodes.
The grade of graphite deposits varies widely, their utilization being largely dependent on the size of the grains and the ease of concentration. Some of the richest deposits, those of Madagascar, contain 20 per cent or more of graphite. The United States deposits contain only 3 to 10 per cent. The graphite situation is complicated by the differences in the quality of different supplies. Crucibles require coarsely crystalline graphite, but pencils, lubricants, and foundry facings may use amorphous and finely crystalline material.
The largest production of high-grade crucible graphite has come from Ceylon, under British control, and about two-thirds of the output has come to the United States. The mines are now worked down to water-level and costs are increasing.
In later years a rival supply has come from the French island of Madagascar, where conditions are more favorable to cheap production, and where reserves are very large. French, British, and Belgian interests are concerned in the development of these deposits. The quality of graphite is different from the Ceylon product; it has not found favor in the United States but is apparently satisfactory to crucible makers in Europe. Most of the output is exported to Great Britain and France, and smaller amounts to Germany and Belgium.
Less satisfactory supplies of crystalline graphite are available in many countries, including Bavaria, Canada, and Japan. Large deposits of crystalline material have been reported in Greenland, Brazil, and Roumania, but as yet have assumed no commercial importance.
Amorphous graphite is widely distributed, being produced in about twenty countries,—chiefly in Austria, Italy, Korea, and Mexico. Certain deposits have been found to be best for special uses, but most countries could get along with nearby supplies.
A large part of the world's needs of crucible graphite will probably continue to be met from Ceylon and Madagascar, while a large part of the amorphous graphite will come from the four sources mentioned.
The United States has been largely dependent upon importations from Ceylon for crucible graphite. Domestic supplies are large and capable of further development, but for the most part the flake is of such quality that it is not desired for crucible manufacture without large admixture of the Ceylon material. Restrictions during the war required crucible makers to use at least 20 per cent of domestic or Canadian graphite in their mixtures, with 80 per cent of foreign graphite. This created a demand for domestic graphite which caused an increased domestic output. Most of the production in the United States comes from the Appalachians, particularly from Alabama, New York, and Pennsylvania, and smaller amounts are obtained from California, Montana, and Texas. One of the permanently beneficial effects of the war was the improvement of concentrating practice and the standardization of output, to enable the domestic product to compete more effectively with the well-standardized imported grades. Whether the domestic production will hold its own with foreign competition under peace conditions remains to be seen. Domestic reserves are large but of low grade.
The Madagascar graphite, in the shape and size of the flakes, is more like the American domestic graphite than the Ceylon product. Small amounts have been used in this country, but American consumers appear in general to prefer the Ceylon graphite in spite of its greater cost. The Madagascar product can be produced and supplied to eastern United States markets much more cheaply than any other large supply; and, in view of the possible exhaustion of the Ceylon deposits, it may be desirable for American users to adapt crucible manufacture to the use of Madagascar material as has already apparently been done in Europe.
Expansion of the American graphite industry during the war, and its subsequent collapse, have resulted in agitation for a duty on imports of foreign graphite.
Amorphous graphite is produced from some deposits in the United States (Colorado, Nevada, and Rhode Island), but the high quality of Mexican graphite, which is controlled by a company in the United States, makes it likely that imports from this source will continue. Since the war the Mexican material has practically replaced the Austrian graphite in American markets. The output of Korea is divided between the United States and England.
Artificial graphite, in amounts about equal to the domestic production of amorphous graphite, is produced from anthracite or petroleum coke at Niagara Falls.