burrstones and chaser mills are being supplanted by grinding equipment of an entirely different type.

The value of the millstones (burrstones) and related quarry products chasers, dragstones, and pavers-sold by producers in the United States in 1923 was a little more than in 1922, but less than in 1921 and other recent years.

In 1919 to 1922 as the output and number of producers decreased in other States they increased in New York.

Value of millstones, chasers, and dragstones sold by producers, 1919-1923

1919: Alabama, North Carolina, Pennsylvania, and Virginia. 1920: Alabama, Maryland, North Carolina, and Virginia. 1921: Alabama, New Hampshire, North Carolina, and Virginia. 1922: Alabama, North Carolina, and Virginia. 1923: Maine, Minnesota, North Carolina, and Virginia.

GRINDSTONES AND PULPSTONES

Grindstones and pulpstones are made from sandstone in northeastern and eastern Ohio, western West Virginia, eastern Michigan, and during the last few years in Pierce County, Wash. In 1923 there was a notable increase in the total quantity of grindstones and pulpstones, as compared with 1922 and 1921, though not as compared with 1919 and 1920. The total value of such stones sold by producers in 1923 was $1,689,315.

Grindstones and pulpstones sold by producers, 1919–1923 a

Oilstones were produced from novaculite quarried in Arkansas, whetstones and scythestones from sandstone quarried in Ohio and Indiana, scythestones from schist quarried in Vermont and New Hampshire, and rubbing stones from sandstone quarried in Indiana and Ohio. Sales of natural hones were reported by only one firm in Kentucky. Most of the output of this group as reported to the Geological Survey consisted of oilstones from Arkansas; next in rank were scythestones from New Hampshire, Vermont, and Ohio.

The output of oilstones, whetstones, hones, scythestones, and rubbing stones for the last five years has been as follows: 1919, 1,463 short tons, valued at $235,943; 1920, 1,144 tons, $231,747; 1921, 831 tons, $173,025; 1922, 1,016 tons, $197,450; 1923, 1,223 tons, $231,812.

CORUNDUM AND EMERY

The domestic sources of emery are in the Peekskill region, N. Y., and Pittsylvania County, Va. The good emery in the deposits formerly worked in the vicinity of Chester, Hampden County, Mass., appears to be exhausted.

Corundum resources were formerly exploited in a large number of localities in the Appalachian section of North Carolina and Georgia. There has been no regular production of corundum in the United States since 1906, although small lots were mined and sold during the World War. In 1923 the production of emery recovered from the severe slump of 1921 and 1922 and nearly reached the quantity recorded in 1919 and 1920.

Although domestic emery does not enjoy the reputation for high quality accorded to Grecian and Turkish emery, it nevertheless appears to be very satisfactory for certain grinding and polishing operations.

A valuable article on the marketing of emery and corundum, by H. A. Plusch, was published in the Engineering and Mining JournalPress, August 30, 1924, pages 339–340.

The emery sold or used by producers, in the last five years, has been as follows: 1919, 2,601 short tons, valued at $23,203; 1920, 2,327 tons, $21,685; 1921, 305 tons, $2,250; 1922, 1,468 tons, $17,511; 1923, 2,286 tons, $29,478.

GARNET

Abrasive garnet is produced in Warren and Essex counties, N. Y.; Merrimack County, N. H.; and Clay and Jackson counties, N. C. In former years a little was produced in Pennsylvania and Connecticut. The principal producing region is Warren County, N. Y. In 1923 the output of abrasive garnet rose to an unprecedented figure, and the average value at the mines was approximately $76 a ton. The figures indicate an unusual growth in the use of garnet as an abrasive material and the recognition of the peculiar worth of garnet in certain finishing processes, especially wood and leather finishing and in shoe manufacturing. In these processes garnet is used chiefly on paper or cloth in the form of ordinary sandpaper and on belts and specially shaped forms.

Recent articles describing garnet resources, methods of mining and preparation, uses, and marketing will be found in the Canadian Mining Journal, July 18, 1924, pages 685-686, and in the Engineering and Mining Journal-Press, October 4, 1924, pages 525-532.

The garnet sold or used by producers in the last five years has been as follows: 1919, 4,944 short tons, valued at $310,131; 1920, 5,476 tons, $434,425; 1921, 3,048 tons, $260,687; 1922, 7,054 tons, $566,879; 1923, 9,006 tons, $688,437

TRIPOLI

The material called tripoli in the trade in the United States is a white, yellowish, or pinkish, light, porous, absorbent, and generally pure siliceous rock that has resulted from the leaching of calcareous

material from highly siliceous limestone or highly calcareous chert, or from the leaching of fine-grained siliceous shale by a process that leaves only silica, or from the chemical weathering and disintegration of novaculite. In its origin and properties and in some of its uses tripoli is like "rottenstone," a small output of which is here reported with tripoli. The "rottenstone" produced in Pennsylvania and also " rottenstones" from England and Scotland appear on examination to be essentially very fine-grained argillaceous material and therefore quite different from tripoli in composition.

The principal commercial sources of tripoli are southwestern Missouri, southeastern Oklahoma, and southern Illinois. The occurrence of tripoli is also known at several localities in the Appalachian region of the Southern States, especially in Tennessee and in Georgia, where there has been some production. Tripoli is also abundant in the Ozark Mountain region of Arkansas.

Some of the Missouri-Oklahoma tripoli is produced primarily for use as an abrasive, but most of it is mined to be worked up into filter blocks, the cuttings and waste from the making of which are ground and prepared for abrasive and other uses. A large part of the Missouri output is also used as filler, for foundry facings, and in many other ways. The Illinois product is generally known simply as "silica," and though used to some extent as an abrasive for metal polishes, in soaps, and in cleansers, it is very largely used in paint and fillers, in making glass, in the body and enamel of ceramic wares, and for facing foundry molds.

The properties, occurrence, history, preparation, and uses of tripoli are described in an article by P. B. Butler and G. V. B. Levings in the Metal Industry, January, 1924, pages 10-14.

It is not possible to determine the amounts of tripoli used as abrasive material and otherwise, nor to obtain from the producers uniform reports on the quantity and value of the crude or rough quarried material, as they sell much of the product originally in some manufactured or prepared form. Statistics herein reported and in earlier chapters of Mineral Resources therefore do not permit satisfactory comparison between years or between producing States.

In the following table the value assigned for crude material is estimated by the Geological Survey; the other figures are reported by the producers.

The output and the value as sold (crude and finished) for 19191921 were as follows: 1919, 24,292 short tons, $181,541; 1920, 40,233 tons, $569,677; 1921, 12,340 tons, $213,013.

DIATOMACEOUS EARTH

Diatomaceous earth, also called infusorial earth and sold under various trade names, is a light earthy material which as obtained from some sources is loose and powdery, and from others is more or less firmly coherent. Much of it resembles chalk or clay, but it can be distinguished at once from chalk by the fact that it does not effervesce when treated with acids. It is generally white or gray but may be yellowish, pinkish, or brown, owing to the presence of impurities, or even black when mixed with much organic matter. Diatomaceous earth is made up of the remains of minute aquatic plants and is composed chemically of hydrous silica.

Deposits of diatomaceous earth are widespread in many parts of the Western States, particularly California, Idaho, Oregon, Washington, and Nevada, where in some places it occurs in very thick beds which are remarkably uniform and pure. Diatomaceous earth is also widespread in beds underlying the coastal region of Maryland and Virginia, occupying the triangular area roughly marked by Annapolis on the northeast, Richmond on the southwest, and the Dismal Swamp region on the southeast. In this region, however, the beds vary in quality or degree of purity and in thickness and are not known to be continuous, though some excellent diatomaceous material has been found within the region. In the northern part of the United States, especially that part geologically known as the glaciated region, and also in the lake region of Florida, diatomaceous deposits on lake bottoms or beneath accumulations of muck in swamps are also abundant.

At present the production of diatomaceous earth in the United States is practically limited to the thick beds of pure earth in California, Oregon, Washington, and Nevada. A little is produced in New York and Maryland and at irregular intervals in several other States.

The diatomaceous earth sold or used by producers in the last five years has been as follows: 1919, 42,642 short tons, valued at $531,960; 1920, 61,922 tons, $1,079,693; 1921 (partly estimated), 55,134 tons, $682,616; 1922, 44,761 tons, $386,669; 1923, 65,833 tons, $699,406.

PUMICE

The domestic product sold as pumice is almost wholly a finely fragmental volcanic glass or so-called volcanic dust or "ash." This material is dug from deposits in which it is interbedded with other sedimentary materials or from deposits of "ash" that blanket the surface. The principal sources of production are in Kansas and Nebraska, but small quantites have been produced in California and other Western States. The domestic production in recent years has included also some lump pumice produced in Arizona and California. This lump pumice is fairly comparable with the imported Italian pumice, which formerly constituted the bulk of the pumice used in this country. Much of the Italian pumice was crushed and

ground for use in the form of powder, and in that state it was not appreciably different from the domestic volcanic dust or "ash," which is a satisfactory substitute for it.

The pumice sold or used by producers in the last five years has been as follows: 1919, 36,051 short tons, valued at $116,835; 1920, 41,838 tons, $114,433; 1921, 37,108 tons, $158,540; 1922, 45,262 tons, $175,600; 1923, 56,575 tons, $214,169.

PEBBLES FOR GRINDING

The production of pebbles used for grinding minerals, ores, and cement ingredients and clinker, and for other purposes, together with the output of quartzite blocks for use as tube-mill liners, reported below, includes only the output of beach pebbles in southern California and of cut cubes or pebbles and liners made of quartzite in Minnesota. The figures appear to cover the entire commercial output, but there was doubtless an unrecorded additional production for local use by the producing concerns.

The production in 1923 showed a considerable increase over that of 1922 and was more than four times that of 1921. It was nevertheless far below the output during the years 1917-1920, when efforts of domestic producers were stimulated by a threatened shortage of the supply of imported pebbles during the period of the war.

The figures for the last five years are as follows: 1919, 9,448 short tons, valued at $85,302; 1920, 10,924 tons, $77,823; 1921, 989 tons, $14,637; 1922 3,159 tons, $30,798; 1923, 4,551 tons, $51,795.

Not separately classified prior to new tariff, Sept. 22, 1922.

The figures for millstones and burrstones may be divided as follows: Rough, 1920, $9,007; 1921, $3,075; 1922, $7,412; 1923, $17,214; made into millstones, 1920, $11,947; 1921, $10,481; 1922, $7,944; 1923, $2,888.