Chapter XX: Emery and Corundum

BY FRANK J. KATZ

USES OF EMERY AND CORUNDUM

Corundum is the natural (mineral) crystalline oxide of aluminum. Emery is a very fine-grained and intimate intergrowth of corundum and other minerals, chiefly magnetite, some varieties containing also important amounts of hematite, spinel, and chlorite. Both emery and corundum are very hard, and break into rough, sharp grains; hence they are used as abrasives for grinding, dressing, and polishing metals--chiefly iron and steel--and glass, and, to a less extent, stone, wood, and other materials. Emery and corundum are used loose in the form of grains, powders, and flours, and also as grains made up into solid wheels, cylinders, blocks, and files of many shapes by means of a great variety of binders. The essential uses are in work on iron and steel and glass. The softer metals and other materials can be worked in many cases to better advantage with other abrasives, such as quartz, tripoli, garnet and pumice.

The essential operations for which emery and corundum are used can be performed with the artificial carbide and alumina abrasives. For some work, however, such substitutions appear not to be advisable, as the abrasive quality and efficiency of both the natural and artificial abrasives depend not only on the hardness of these materials, but also on a number of other factors: among these being the physical qualities of the materials worked; the sharpness of edges and angles of broken particles of the abrasive; the manner in which the abrasive breaks down under use; the manner of, and materials used in, binding the abrasive particles; and the speed and pressure with which they are applied to the work.

Of the various kinds of material abraded, each calls for different grades and kinds of abrasives, and for variation in the above factors in the use of these abrasives in order to insure most efficient use. Consequently, it is almost impossible to determine arbitrarily the uses for which each of the various abrasive materials is essential. This much, at least, seems certain--that for finishing and polishing glass, particularly optical glass and plate glass, there is as yet no general agreement that satisfactory substitutes are available for the better grades of Turkish and Greek emery, although experiments in manufacture and use of suitable artificial abrasives have been successful.

GEOLOGICAL DISTRIBUTION

The known emery deposits are products of magmatic differentiation or of regional metamorphism, or of combined contact and regional metamorphism of limestone, presumably argillaceous, and of argillaceous sediments. A study of certain individual deposits, therefore, makes possible some forecast as to future supplies in some regions, particularly those in which the emery deposits are intimately related to certain beds in metamorphic sedimentary formations in close proximity to igneous rocks. The emery bodies are, however, as a rule, spotted or irregularly distributed, and reliable estimates of reserves are difficult.

Corundum, in a number of associations, is an original constituent of a great variety of igneous rocks, such as peridotites, anorthosites, syenites, nepheline syenites, and syenite pegmatites. It is also abundantly found in regionally metamorphosed rocks and in contact metamorphic zones, occurring in serpentines, mica schists, quartz schists, and crystalline limestones. A third important source of corundum is alluvial deposits. Corundum is not a characteristic or essential constituent in any of these types of rocks and is present in alluvial deposits in restricted localities only. Furthermore, its distribution and its concentration, when present, are irregular and unsystematic, and there are, therefore, no geologic guides by which future supplies can be forecast without intensive study of each individual occurrence.

GEOGRAPHIC DISTRIBUTION

The chief deposits of emery and corundum in the _United States_ are in the eastern seaboard or Appalachian states.

The emery deposits of Chester, Massachusetts, are in a narrow band less than 500 feet wide that has been traced for nearly five miles. The Chester deposits have been worked at various times since the eighties and up to 1913.

Emery deposits near Peekskill, New York, are associated with igneous rocks in an area of 20 to 25 square miles. These deposits have been worked since 1889. Some of the material mined is a true emery, that is, an intimate mixture of corundum and magnetite, but most of it is largely a mixture of spinel and magnetite, which, while not a true emery, makes an excellent abrasive. In 1916 and 1917, the annual output of ore was approximately 15,000 tons.

In the vicinity of Whittle, Pittsylvania County, Virginia, spinel emery, somewhat like the New York emery, but containing more corundum, is abundant. The deposits in this region have already produced considerable emery and may be counted on for a large supply.

Corundum is associated with a serpentine belt extending through Lancaster, Chester, Delaware, Montgomery, and Bucks counties, Pennsylvania, and through adjoining counties in Delaware and Maryland. The deposits in this region do not seem to be of commercial importance.

Corundum is found in a large number of localities in North Carolina. The most important occurrences of corundum are in or near peridotite masses, also in schists, and in alluvial deposits. Active mining work was first begun in 1871 and continued until about 1906, when North Carolina corundum was driven from the market by the competition of Canadian corundum and artificial abrasives. Corundum mining was revived in 1915, and the three properties worked in 1917 made an output of 820 tons. There is unquestionably a very large reserve of corundum in this region, but transportation is difficult and efficient labor is scarce; so that there is little immediate prospect of a large development.

The only commercially important deposits of abrasive corundum west of the Appalachian Mountains are in the central part of Gallatin County near Salesville, Montana, where corundum occurs in syenite and syenite pegmatite. The deposits have been worked by three companies, and up to 1903, when operations ceased, had produced several hundred tons of corundum.

The sources in _Canada_ of abrasive corundum of commercial importance are limited to the corundum syenites and anorthosites in central Ontario. These deposits have been developed and mined only at the Burgess mines and at Craigmont. Corundum mining as an industry in Canada began in 1900. The production reached a maximum in 1906 and was smaller and fairly uniform from 1907 to 1913, in which year operations were practically suspended.

The reported occurrences of corundum in _Mexico_ and _Central and South America_ are chiefly of the gem variety. Emery is reported from Musco, Colombia, and common corundum is reported as especially abundant at localities in the State of Sao Paulo, Brazil.

The only occurrence of emery and corundum of commercial importance in _Europe_ is in the islands of the Grecian Archipelago, particularly the Island of Naxos. The deposits occur there as lenses and masses in limestones and in the vicinity of granites. Exploration and development work has been superficial, but reserves or future supplies there are probably enormous. Annual exports during the years 1897 to 1914 averaged 6,800 metric tons.

In _Asia_ there are commercial corundum deposits in Asiatic Turkey and in India.

The emery deposits of Asiatic Turkey are near Smyrna. The Turkish emery is similar in origin and general character to the Greek emery, except that none is found in Asia Minor of quite the superior quality of that of Naxos. The main source of supply seems so far to have been from the detrital deposits. It seems almost certain that supplies are large. The emery mines of Asia Minor are very old and have annually contributed large quantities to the world’s supply, their output having been larger than from any other region in the world. Statistics for recent years are lacking. The recorded output in official reports of the Turkish government was about 62,000 metric tons in 1908 and about 25,000 in 1909.

The corundum deposits of India are numerous and include not only the common abrasive varieties but also the most highly prized gem varieties. Commercially important deposits of the abrasive variety occur in the presidency of Madras. The following provinces and native states also contain the mineral in more or less abundance: Afghanistan, Bengal, Burma, Central Provinces, Punjab, and Travancore.

Available data on the production of corundum in India indicate an output between 100 and 500 long tons a year, up to and including 1915. In 1916 the production was approximately 2,000 long tons and since then it has probably equaled or exceeded that figure. Nothing definite is known as to the corundum resources of India, except that they are undoubtedly large.

The only recorded deposits of abrasive corundum in commercial quantities on the continent of _Africa_ are in the vicinity of Pretoria, in the Transvaal, where corundum, probably occurring originally in schists, is concentrated from residual material on the land surface. Little information concerning these corundum deposits is available, but it is probable that large reserves may be developed. The production, which had been slight or negligible prior to 1912, expanded greatly in 1917 to about 3,000 long tons.

Corundum appears to be abundant on the Island of Madagascar, where large amounts of gem stuff and abrasive materials have been found in alluvial deposits. The production of abrasive corundum, which was very small in 1910, expanded to about 1,100 metric tons in 1913, and approximately 1,000 metric tons in 1916.

DEVELOPMENTS AND CHANGES IN THE NEAR FUTURE

No material changes in geographic distribution of resources appear probable in the near future. None of the deposits now productive is approaching exhaustion, and only concerning emery in Virginia, where somewhat larger emery production may be expected, is information at hand upon which to forecast changes in output.

Substitution of artificial abrasives for emery and corundum may be extended. Experiments conducted early in 1918 looking toward the development of an artificial abrasive suitable for use in optical and plate-glass work have been successful, so that there may remain no industrial operation wholly dependent on emery and corundum. The complete supplanting of the natural abrasives, however, will depend in part on the supply of bauxite available for manufacture into artificial abrasives. At present the United States supplies of bauxite are sufficient for such use.

The demand in Britain and France for Indian and South African corundum and Greek emery would undoubtedly diminish if the French artificial abrasive plants were in full operation. Such a change would also probably cut down exports of artificial abrasives from the United States, and correspondingly affect the demand for emery and corundum.

POLITICAL CONTROL

Emery and corundum resources within the United States are owned, so far as known, by American citizens, and are in no way state controlled.

The Greek emery industry was formerly a monopoly controlled by the Greek government, but the inhabitants of the emery region had always maintained their sole right to mine the emery. This right was respected, and the Greek government merely regulated and managed sales and exports, exacted high royalties, which were changed from time to time, fixed prices, and maintained high quality and uniform standards of emery for export. The French government during the war assumed control of the Naxos emery supply and presumably continued the regulations of the Greek government. Supplies of Greek emery were available only to France and her allies, through allocation by the French government.

COMMERCIAL CONTROL

In the United States the various emery and corundum deposits are in small holdings that are mostly owned by local residents. The mines and quarries have been worked by lessees on royalty, generally. A considerable number of operators are and have been engaged in several localities, and there are no trade coalitions. Crushing and grading are in the hands of eight independent competitive companies, except in so far as they were welded during the war into a trade association by the War Trade Board for the purpose of allocating, under Government supervision, the small imports of Greek emery to essential industries.

In Canada the better portions of the corundum deposits seem to be controlled largely by one company--Manufacturers Corundum Co.--whose owners seem to be dominantly or entirely of Canadian nationality.

The Greek emery deposits, particularly those of Naxos, are claimed to be the inalienable property of the families resident upon the island.

There is no control of emery and corundum resources through ownership of crushing, milling, and grading plants, nor through patents or secret processes of preparation. Trade combinations as affecting emery and corundum supply are unknown. There are a number of milling companies in the United States, Britain, France, and Germany, who compete for the world’s supply of raw material, and those of each country compete with one another for markets for the graded, prepared material.

POSITION OF THE NATIONS

The _United States_ has supplies of inferior emery and resources of corundum which are not developed adequately to meet the demands for natural abrasive materials. During the war the United States was short of the amount of emery and corundum desired by consumers. However, this shortage was offset by an excess supply of artificial abrasives.

_England_, in India and South Africa, has corundum supplies probably more than sufficient for her needs. England is probably well enough supplied with these abrasives, particularly as long as she continues to import from Canada and the United States the needed artificial abrasives.

_France_ has no home supply of emery and corundum, but has large resources in her colony, Madagascar, and during the war controlled the Greek emery supply. Furthermore, France has in reserve rich bauxite deposits and hydro-electric power for manufacture of artificial abrasives.

_Germany_ depended upon Turkish emery during the war. She is short of bauxite, but makes large quantities of carborundum.

_Japan_ probably can supply her needs by drawing on Indian corundum resources and on the United States for artificial abrasives. During the stringency of supply in 1917 some material was exported to the United States from Japan.

SUMMARY

Corundum and emery, the latter a close association of corundum with certain other minerals, are used as abrasives for grinding and polishing metals, glass, stone, and wood. Many of the operations formerly performed with emery and corundum are now being performed with artificial carbide and alumina abrasives.

The deposits of emery and corundum are few in number, but their product is ample for all present needs. Commercially important deposits are situated in the Appalachian region of the United States; on the islands of the Grecian Archipelago, especially the Island of Naxos; in the Province of Aidin, in Asia Minor; in the presidency of Madras and the provinces of Punjab, Bengal, and Travancore, India; in Madagascar; and in the Transvaal near Pretoria.

The geological formation of emery and corundum deposits makes impossible any accurate estimate of reserves or any forecast of future discoveries.

The political control of the emery and corundum resources of the world corresponds to the geographical location except as regards the deposits on the Island of Naxos. This island is Grecian territory, but the French government during the war assumed control of the emery industry and allocated supplies of the abrasive only to the industries of France and her allies. The deposits of Asia Minor are at present (1920) nominally in the control of Turkey, but actually partly in the coastal strips seized and held by the Italians and the Greeks after the armistice. Madagascar is a French possession, and the Transvaal and India are parts of the British Empire.

The deposits of the United States are owned by a number of small independent operators, all American as far as is known. The Canadian deposits are controlled largely by one company, the Manufacturers Corundum Co., whose owners are predominantly or entirely Canadian. The Greek emery deposits, particularly those of Naxos, are claimed to be the inalienable property of the families resident on the island.

TABLE 64.--PRODUCTION OF EMERY AND CORUNDUM, 1910-1917

--------------------------+-------------------------------------
| Emery | Corundum
----+------+-------+------+------+-------+------+-------+-------
|United| | |United| | | Mada- |So.
|States| Greece| |States| Canada| India| gascar|Africa
| [149]| [149] |Turkey| [149]| [149] | [149]| [149] | [149]
----+------+-------+------+------+-------+------+-------+-------
| | Ore | | | | | Grains| Grains
| Ore |shipped| |Grains| |Grains| or ore| or ore
| pro- | from | | pro- | Grains| pro- | pro- | pro-
| duced| Syria | | duced|shipped| duced| duced | duced
| (long|(metric| | (long| (long | (long|(metric| (long
| tons)| tons) | | tons)| tons) | tons)| tons) | tons)
----+------+-------+------+------+-------+------+-------+-------
1910| 940| 12,939| [150]| [151]| 1,660 | 218| 11 | [150]
1911| 620| 9,845| [150]| [151]| 1,270 | 275| 150 | [150]
1912| 870| 7,687| [150]| [151]| 1,600 | 345| 496 | 99
1913| 900| 1,440| [150]| [151]| 1,090 | 355| 1,099 | [150]
1914| 460| 10,226| [150]| [151]| 500 | 105| 556 | [150]
1915| 2,840| [150]| [150]| [152]| 220 | 62| 327 | [150]
1916|14,400| [150]| [150]| [152]| 60 | 1,868| 914 | [150]
1917|15,400| [150]| [150]| 770 | 160 | [150]| [151] | 4,051
| | | | | | | | [153]
----+------+-------+------+------+-------+------+-------+-------

[149] Statistics for United States from U. S. Geol. Survey; for
Canada, Canada Dept. Mines; for Greece, British Consular Reports
quoted in “Mineral Industry;” for India, Records India Geol. Survey;
for Madagascar, Service des Mines, Madagascar; for South Africa,
American Consular Reports.

[150] Figures not available.

[151] No production.

[152] Small unrecorded amount.

[153] Nine months, Jan.-June and Oct.-Dec.