For punch mica the uncut sheet must be of sufficient size to yield a circle 11⁄2 inches in diameter if stained and 14 inches if clear; circle mica should yield a disk nearly 2 inches in diameter.

Canadian or "amber" mica is also classified on the basis of the size of the rectangle obtainable, but the sizes differ from those used for the United States mica. The sizes used for Canadian mica, in inches, are 1 by 1, 1 by 2, 1 by 3, 2 by 3, 2 by 4, 3 by 5, 4 by 6, and 5 by 8.

The Indian classification is not based on the size of the rectangle obtainable but on the area of usable mica in the sheet. The following table shows the Indian system of grading, with the approximate corresponding sizes used in the United States classification:

In the following table about 80 per cent of the total quantity of uncut sheet mica sold in 1923 has been classified to show the qualities of mica and the average value by sizes. It was not possible to classify a larger percentage, for the reason that some of the reports received by the Geological Survey did not contain this information. Several of the larger companies have sent in returns in great detail, but others have not done so, owing in part to the fact that some mica is not sold by the miner in sheet form classified by sizes and also to the fact that some of the companies either do not keep an accurate account of the mica they handle or do not wish to furnish the figures. Clear and stained uncut rough-trimmed sheet mica produced in the United States and sold in 1923, by sizes

[Shows about 80 per cent of the total for the United States]

1919.

1920.

1921. 1922

Value of mica sold by producers in the United States, 1919–1923a

1923.

a The figures for sheet mica in 1920-1923 are not strictly comparable with those for earlier years, as they represent uncut sheet mica exclusively. Prior to 1920 some cut sheet mica was included.

Mica prices during 1923 on the whole showed small variation. The prices for the smaller sizes of sheet mica tended to decrease in the last half of the year, while the prices for the sizes larger than 2 by 2 inches showed varying increases for the same period. In the first half of 1924 prices of uncut-sheet mica were slightly higher than for the preceding six months and were more stable.

WORLD'S PRODUCTION 1

World's production of mica, 1914-1923, in metric tons

• Sources of information-Canada: 1914-1920, Dept. Mines, Mines Branch, Ann. Repts.; 1921, Dominion Bur. Statistics, Ann. Rept.; 1922-1923, Dominion Bur. Statistics, Prel. Repts. Argentina: 1914-1918, Estadística minera; 1919-1922, data furnished by Dirección general de minas, geología é hidrología. Brazil: Commercio exterior do Brasil. Norway: Norges Handel. Rumania: Statistique minière de la Roumanie. Russia: Gornyi Zhurnal, Nos. 3-4, 1923, Moscow. Spain: Estadística minera de España. Sweden: Sveriges officiella Statistik, Bergshantering. Ceylon: 1914-1915, Bull. mines de Madagascar; 1916-1918, Imp. Mineral Resources Bur., London; 1919-1923, official data furnished by U. S. consul, Colombo, Ceylon. Chosen: Official data furnished by U. S. consul, Keijo, Chosen. India: Geol. Survey Records. Madagascar: 1914-1921, Rapport, Service des mines; 1922-1923, Bull. des mines, Tananarive. Nyasaland: Imp. Mineral Resources Bur., London. Rhodesia: Sec. Mines Rept. Southern Rhodesia: Chamber of Mines Rept. Tanganyika Territory: Imp. Mineral Resources Bur., London. Union of South Africa: Sec. Mines Ind., Dept. Mines, Ind., Ann. Repts. Australia: Northern Territory, Dept. Mines. Queensland: Under Sec. Mines, Ann. Rept. South Australia: Review of mining operations, Dept. Mines. Western Australia: Dept. Mines, Rept.

Exports.

Less than 1⁄2 ton.

d Data not available.

From early in 1917 to July, 1918, the Uluguru mines were worked by a mica board under military authorities; 17 tons was exported by the mica board. From July, 1918, to March 31, 1920, the civil administration, operating under a mica expert, exported 131 tons.

Estimate by U.S. Geol. Survey based on value reported.

1 Compiled by Miss W. I. Whiteside, of the United States Geological Survey.

World's production of sheet mica, 1914-1923, in metric tons

1914-1920, estimated, by U. S. Geol. Survey as one-half of the total reported production of mica in Canada; 1921-1923, figures for sheet mica as published by Dominion Bureau of Statistics.

The total reported production of mica for the other countries incomplete, as no figures of production are available for some of the countries.

•Figures not yet available.

IMPORTS AND EXPORTS 2

The imports of uncut sheet mica in 1923 were 1,044,366 pounds, valued at $532,375. Imports of mica in 1923 were received from 19

countries.

Mica imported for consumption in the United States, 1920-1923

Essentially uncut trimmed sheets.

Includes the Madras square-shaped uncut sheets.

Quantities not recorded prior to ne w tariff, Sept. 22, 1922.

Classification di scontinued with new tariff and items shown separately.

• Sept. 22-Dec. 31.

Not separately classified prior to new tariff.

The import duty on mica as fixed by the tariff act of September 22, 1922, paragraph 208, is as follows:

Mica, unmanufactured, valued at not above 15 cents per pound, 4 cents per pound, valued above 15 cents per pound, 25 per centum ad valorem; mica cut or trimmed and mica splittings, 30 per centum ad valorem; mica plates, and built-up mics, and all manufactures of mica or of which mica is the component material of chief value, 40 per centum ad valorem; ground mica, 20 per centum ad valorem.

The statistical information on imports and exports has been compiled by J. A. Dorsey, of the United States Geological Survey, from records of the Bureau of Foreign and Domestic Commerce, United States Department of Commerce.

Mica imported into the United States in 1922 and 1923, by countries

Quantities not recorded prior to new tariff, Sept. 22, 1922.

Figures showing the consumption of mica splittings in 1923 are incomplete, as some of the companies did not report this information. Mica and manufactures of mica were exported to 46 countries in 1923, but about 88 per cent of the total quantity, which was 1,804,342 pounds, went to Canada, England, and France, in the order named. The total value of the mica exported was $182,162, against $129,186

in 1922.

SAND AND GRAVEL

By A. T. COONS

PRODUCTION

The sand and gravel sold or used by the producers in the United States in 1923 amounted to 139,932,153 short tons and was valued at $90,903,654. These figures show an increase of about 48 per cent in quantity and 41 per cent in value over those for 1922. There was a general increase in both the quantity and the value of all classes of this material except in the value for filter sand. A special canvass of railroad companies was made in 1923 in order to obtain more complete reports of noncommercial material used by them, and the figures obtained make up in part the large increase (146 per cent) shown in the quantity of gravel for railroad ballast. The sand and gravel for use in the construction of buildings and pavements also showed a large increase. Sand for molding increased 45 per cent. The figures for 1923 include returns obtained from 2,428 sand and gravel plants, which is 443 more than the number represented by the figures for 1922.

The production of sand and gravel reported for 1923 is approximately double that for 1919.

Sand and gravel sold or used by the producers in the United States, 1919-1923