pound for Nos. 51⁄2 and 6 half-trimmed heavy-stained to $70 per pound for No. 3 and larger full-trimmed good stained and better, about 4 to 6 times greater than the market price. As of December 31, 1952, a total of 55,515 pounds of fulltrimmed mica was purchased, 66 percent of which originated at the Spruce Pine depot. Of the total poundage, about 26,663 pounds was good-stained and better quality, 23,859 stained, and 4,993 heavy-stained.

TABLE 1.-Yield of full-trimmed mica from domestic purchases by GSA, July– December 1952, by quality, grade, and depot

The Government also has extended purchase contracts for imported mica, including several with Brazilian producers.

The Bureau of Mines, in cooperation with NPA, initiated a quarterly canvass on mica consumption, in order to obtain data not previously available for defense mobilization planning. Industry reported a consumption of 175,821 pounds of good-stained and better mica from July to December 1952. At this rate, only 15 percent of the 1952 consumption of good-stained and better mica could have been supplied by the subsidized domestic mica program and under a war economy consumption probably would be double the 1952 rate. Consumption of stained mica was 1,259,591 pounds and lower than stained was 1,933,734 pounds.

Government and industry have been conducting experiments on mica in an effort to alleviate the shortage of strategic grades and qualities of muscovite sheet mica. The objective of the Bureau of Mines program at Norris, Tenn., since 1947 has been to fabricate and study synthetic fluorine-mica ceramics and to investigate methods for growing crystals and fabricating sheets of synthetic fluorine-mica. Major accomplishments have been (1) development of the direct electric resistance melting technique of manufacturing large quantities of flake mica, (2) synthesis of fluorine-micas by solid-state reaction, (3) development of machinable synthetic mica ceramic dielectrics by hot-pressing and phosphate bonding, (4) invention of synthetic mica-metal cermets and a reconstituted synthetic mica sheet, and (5) discovery of a family of synthetic clay-like compounds that are potential catalysts and bleaching agents.

TABLE 2.-Consumption of muscovite block and film in the United States, JulyDecember 1952, by end uses

Experiments have shown that replacement of the OH ion with F gives synthetic mica superior properties to natural mica and can withstand higher temperatures. The composition of the synthetic mica can be controlled with virtual elimination of iron and other contaminates that lower the Q-factor. A high Q-factor is desirable in a material used in capacitor circuits. Results show that hot-pressed synthetic mica is comparable to the best commercial ceramic dielectrics. There has been increased interest by industry in this material as a matrix for silicon carbide and as a mica ceramic for jet engines. Reconstituted mica sheets of controllable thickness and uniformity have been produced from synthetic mica and show promise as a possible substitute for sheet mica. The mechanical strength of such sheets has been improved significantly by bonding normal fluor-phlogopite mica to boron-phlogopite mica. Recently, a company advertised the availability of synthetic mica in trial and semiproduction lots. The production of this material was a direct outgrowth of the Bureau of Mines program on synthetic mica.

Recent developments by two commercial firms permit the use of domestic scrap mica in the production of reconstituted mica in long continuous sheets or rolls. This new product provides the electrical designer with a new and improved electrical insulation for applications now using built-up mica, made with imported splittings. Further development of this material may relieve our country of its dependence on India for our annual supply of splittings. However, in order for the Indian mica industry to operate profitably, a market must exist for the splittings obtained in the preparation of block and film mica, or the prices of block and film mica would have to be increased.

STOCKPILE

The following categories of mica are being stockpiled: Muscovite block, good ined and better; muscovite block, stained; muscovite film; phlogopite block;

muscovite splittings; and phlogopite splittings. The objective has been met for both varieties of splittings. Purchase of the other classes is continuing to meet the established objectives.

RESERVES

Because of the sporadic nature of the mica deposition, it is almost impossible to estimate reserves of strategic mica in the Western Hemisphere. The best reserve estimates show the northern section, principally the United States and Canada, to be bad in reserves. Brazil has the best reserves in the Western Hemisphere, but can only be classified as slightly better than bad.

IMPORTS

The United States depends on foreign sources for high-quality sheet mica. Most strategic muscovite mica block, film, and splittings imports into the United States have come from India.

Brazil is second to India as a source of strategic qualities of muscovite. Many authorities on the mica industry consider it potentially as important as India. The best known and most accessible mica-producing areas in Brazil are in the State of Minas Geraes. Import records show that the United States imported from Brazil 197,768 pounds of good stained and better block and film and 1,389,311 pounds of stained in 1952. This represented 30 and 69 percent, respectively, of the total United States imports. Mica imports from Brazil are averaging $13.50 per pound for good stained and better mica, as against $27 for good stained and better domestic mica sold to the Government. The mica industry in Brazil is very primitive and lacks modern equipment and technical management, and is further handicapped by high interest rates. It is anticipated that mica production in Brazil will decrease in the next few years unless aid is given to the mica industry. In an emergency, Brazil could serve as a vital factor in our supply of strategic block and film mica.

TABLE 3.-Muscovite block and film mica, United States general imports, by qualities and principal sources, 195218

1 Compiled by the U. S. Tariff Commission from official documents of the U. S. Bureau of Customs. 2 Does not include imports from Angola, Austria, Port of East Africa, and Northern Rhodesia because detailed breakdowns from these sources are not available. Imports from these sources totaled 48,350 pounds. Includes imports from Angola, Argentina, Canada, Colombia, Southern Rhodesia, Tanganyika, and United Kingdom.

Includes 1st and 2d quality film.

• Includes other quality film.

TABLE 4.-Muscovite splittings, United States general imports, by form and principal sources, 19521

1 Compiled by the U. S. Tariff Commission from official documents of the U. S. Bureau of Customs. * Includes imports from Brazil and Mexico.

TABLE 5.-Phlogopite splittings, United States general imports, by
principal sources, 19521

Country:

Madagascar-
Other 2

Quantity 677, 688 1,084

Total____

678, 772

1 Compiled by the U. S. Tariff Commission from official documents of the U. S. Bureau of Customs. Includes imports from Canada and Mexico.

TARIFF

Depending on state of manufacture and size, duties range from 2 cents per pound plus 15 percent ad valorem up to 40 percent ad valorem.

Efforts to reduce the dependency of the United States on foreign sources of strategic mica should be concentrated on the following:

1. Intensified research on growing synthetic mica crystals, including fundamental studies of crystal defects and their correlation with the effect of physicalchemical environment on growth, together with further investigations for the control of crystallization.

2. Perfection of feasible and efficient methods for the delamination-relamination of synthetic flake mica for builtup mica, especially for electronic uses.

3. Encouragement of the expansion of free-world mica production, especially from Brazil, through technical assistance and a supply of equipment now not available to the miners, on a rental basis, or through financial assistance for purchase of such equipment.

4. Continuation of the evaluation of domestic mica resources with special reference to mining and processing techniques, economics, and the potential recovery of coproducts and byproducts.

5. Continuation of mica purchases for the stockpile from domestic and foreign

sources.