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.