MONAZITE, THORIUM, AND MESOTHORIUM
BY R. B. MOORE
USES OF MONAZITE
Practically the only use of monazite has been as a source of thorium
salts. In extracting these, by-products are recovered, such as cerium,
lanthanum, and other rare earths. Thorium salts are used almost
exclusively for the manufacture of Welsbach mantles, which consist of
99 per cent. thorium oxide and 1 per cent. cerium oxide. For this use
there is no known substitute. The one other use of thorium salts is
in ordinary chemical laboratories, but this use is very limited. The
fluoride and other salts of cerium are used in connection with the
flaming arc, their presence giving increased luminosity.
Mesothorium is a radio-active element always found in thorium minerals.
Until quite recently it has been thrown away in the manufacture of
thorium nitrate; but it is now being produced as a by-product, and
is useful as a substitute for radium in luminous paints, and for
therapeutic purposes.
GEOLOGICAL AND GEOGRAPHICAL DISTRIBUTION
The principal sources of monazite are Brazil and India, although it
has been mined successfully in the United States in the Carolinas and
in Idaho. It has been found in Swaziland, Africa, and in Australia,
and also, to a limited extent, in native rock and in placers in
Ekaterinburg, Russia.
Monazite is usually found in the gravels of small streams or bottom
lands, although it is sometimes found in the soil of hillsides. In
Brazil and India it occurs mainly in the beach sands of the sea
coast. In places it is found in small crystals in gneiss, granite and
pegmatite rocks. As these rocks become disintegrated, the crystals
are washed into streams and with other heavy sands are deposited in
the stream beds. On the coast of Brazil, the monazite grains from the
crystalline rocks of the coastal mountains are concentrated by the
waves of the sea.
=United States.=--The deposits of the Carolinas cover an area of
several hundred square miles east of the Blue Ridge Mountains.
In North Carolina, the counties of Cleveland, Burke, Alexander,
Rutherford and Lincoln furnish the richest deposits. In South Carolina
the only deposits of value are in the counties of Cherokee and
Greenville. Practically all of the monazite mined in the Carolinas is
derived from gravels in streams and bottom lands, the miners usually
following the stream courses. The gravels vary greatly in thickness,
and it is therefore difficult to make a true estimate of the average,
but in general the monazite-bearing gravels are between 1¹⁄₂ and 2¹⁄₂
feet thick. The top soil in the bottom lands averages 3 to 6 feet thick
and may be 7 feet or more.
The deposits in the State of Idaho are near Centerville and Idaho
City. In the future, under more favorable conditions of price,
transportation, etc., these deposits may possibly become a commercial
source of monazite. Almost all of them contain small quantities of
gold. The gravel beds are considerably thicker than those in the
Carolinas, and with the gold content might be more profitable were it
not for labor being higher priced.
Monazite has been found in Colorado, in the Newland Gulch district,
20 miles south of Denver, where it occurs in gravels that carry
considerable gold.
=Brazil.=--There are three kinds of monazite sand deposits in Brazil;
the deposits within the government lands along the coast; deposits
lying behind the government coastal lands, which are private state
possessions or belong to private parties; and inland deposits. The bulk
of the monazite is derived from coast sands in the states of Espirito
Santo and Bahia, the sand being washed by means of oscillating tables
or sluice boxes. The coast lands are the property of the federal
government for 33 meters inland, measuring from the point where the
sea waves wash the beach at mean high tide. This uncertain method of
marking property has of course given rise to disputes when boundaries
are established.
At a few places along the coast strips of monazite-bearing sands lie
directly behind the government land, and some of these might be worked
profitably were it not for the fact that it has been difficult to prove
to the federal government that these sands were not taken from the
nearby government land. One French concern has exploited such lands
in the State of Rio de Janeiro. Along the banks of the large rivers,
such as Parahyba, there are great quantities of black sands with traces
of monazite. Near Sapucaia such deposits have been worked by a French
concern. Many of the inland deposits can not be exploited on account of
the expense of transportation of the products, as the deposits are many
miles from a railroad.
=India.=--India is the newest source of monazite sands, the deposits
lying on the sea beach like those in Brazil. The deposits are in
the Travancore district near the southwestern end of the Hindustan
peninsula. Very little information is available concerning these
deposits.
CHANGES IN TREATMENT PRACTICE
The general method of treatment employed until quite recently has
involved leaching the concentrate with concentrated sulphuric acid,
thus getting the thorium, cerium, and other rare earths in solution and
separating them from the silica, zircon, ilmenite and other insoluble
products. From this stage different companies used slight variations in
practice, such variations being kept strictly secret, although they all
involved the precipitation of the thorium as oxalate by means of oxalic
acid.
At the outbreak of the war the price of sulphuric acid went to four or
five times the original cost, and the increased price of oxalic acid
was practically prohibitive. Consequently the manufacturing companies
had to change their entire procedure and to use chemicals that they
could obtain at a reasonable price. In this difficult undertaking the
companies were successful, and at least one company devised a process
that was considerably more efficient than the old one.
At present mesothorium is being produced as a by-product by the Lindsay
Light Co. and the Welsbach Co., the process used by the latter company
having been originated by the Colorado Station of the United States
Bureau of Mines. This process is cheap and extremely efficient, and
will no doubt enable the Welsbach Co. to compete commercially with
any other manufacturer of mesothorium. Of course as the process was
developed by the Bureau of Mines it will ultimately be made available
for anyone, but as mesothorium can only be made at a profit as a
by-product of thorium nitrate, anyone who manufacturers mesothorium
must first establish a thorium industry.
POLITICAL CONTROL
The important monazite resources of the world are controlled
politically by three nations: the United States, Great Britain (India)
and Brazil. The deposits of the United States, in normal times,
probably can not be worked successfully in competition with the foreign
deposits without the protection of a high tariff.
COMMERCIAL CONTROL
=United States.=--The widely scattered monazite deposits of the United
States are of importance only during a period of abnormally high prices
or during the restriction of imports from Brazil and India. The known
reserves are small and the deposits will probably never be an important
factor in the world monazite market. As far as the writer knows, all of
the American deposits are controlled by American capital.
The manufacture of thorium nitrate in this country is closely
controlled by two large companies, the Welsbach Co. and the Lindsay
Light Co.; they own the only two commercial plants of any size in the
United States.
All of the manufacturers of mantles in the United States, with one
exception, must obtain their thorium nitrate from one of these two
companies. As these companies supply practically all the thorium
nitrate requirements of England and France, they control the thorium
industry. The only other manufacturer of thorium nitrate in this
country is the Block Co., of Chicago, which uses about 15 tons of
monazite a year, making sufficient thorium nitrate for its own
production of mantles. The Welsbach Co. uses about 1,200 tons of
monazite annually and the Lindsay Light Co. about half that amount.
The Welsbach Co. has contracts for the delivery of monazite, up to its
requirements, from Brazil; the Lindsay Light Co. has obtained all of
its monazite from India.
Most of the processes used, including those used by the Welsbach Co.
and the Lindsay Light Co., are secret. As thorium can be extracted from
monazite in more ways than one, a secret process does not necessarily
mean commercial control unless such a process is in every way efficient
and the company owning it is willing to get into a commercial war.
=Brazil.=--As the Brazilian deposits have for so many years been the
chief source of the supply of monazite, the history of their commercial
control is practically a history of the commercial control of the
monazite industry. About 27 years ago, John Gordon, an American now
residing in New York, found monazite on the coast of Brazil. He brought
large quantities to Hamburg, Germany, and was able to obtain a monoply
of the monazite sand.
At that time the manufacture of thorium nitrate, the principal
product of the monazite sand, was confined in Europe to a few large
chemical firms in Germany and the Welsbach Co. in Vienna. They not
only supplied the European market with thorium nitrate, but also sent
large quantities to the United States. The American Welsbach Co. early
manufactured thorium nitrates from sands mined in the Carolinas, a
protective duty of 6 per cent. making this possible.
In 1902 Mr. Gordon agreed to supply the four large German manufacturers
and the Austrian manufacturers with monazite at a price of $150 a ton
and a profit on the manufactured nitrates. A close combination thus
formed, known as the German Thorium Convention, prevented other thorium
manufacturers from acquiring any of the mineral mined by Mr. Gordon,
and raised the price of thorium nitrate 100 per cent.
For a considerable period Mr. Gordon exported the sand from the coast
lands of Bahia, near Prado, Brazil, without interference. Finally the
Brazilian government became acquainted with the value of the resources
and decided that no private individual or state government had the
right to mine, sell, lease, or remove any monazite on so-called state
lands without the consent of the federal authorities. In 1908 the
government advertised that coast lands in the State of Espirito Santo
would be leased to the highest bidder for the exploitation of the
sands. A contract was thus obtained for the firm of A. C. de Freitas
& Co., of Hamburg, Germany. By the contract the firm agreed to pay to
the Brazilian government a rental equal to 50 per cent. of the selling
price of the monazite sands and to export at least 1,200 tons annually.
To avoid trouble the German Thorium Convention arranged later that
half of its supply should be furnished by Mr. Gordon and half by the
de Freitas company. A new convention was formed by the four German
chemical manufacturers with Mr. Gordon and the de Freitas company,
preventing firms in other countries that had started to manufacture
thorium nitrate from getting raw material. Consequently great efforts
were made to find and develop new deposits of monazite. The high
price for thorium nitrate made possible the mining of monazite in
the Carolinas and its export to Germany, especially to one German
manufacturer who was not in the German Thorium Convention.
Ultimately there was an overproduction of thorium and in 1906 the price
dropped 50 per cent. Monazite mining declined in all localities where
the cost of mining was high, and production in the Carolinas and the
interior of Brazil practically stopped.
During the four or five years antedating the war the German
Incandescent Gas Light Co., of Berlin, succeeded in controlling the
largest manufacturers of thorium nitrate in Europe, except those in
France. It controlled both the English and Australian companies and
became the active competitor of the so-called Thorium Convention, which
at that time had lost much of its power. Mr. Gordon still has extensive
interests in Brazil, but he does not have a monoply. The exportation
rights from Brazil are in the hands of Luis de Rezende & Co. (Rio de
Janiero), Mr. Gordon, and others. Luis de Rezende & Co. is mainly a
French concern, but has Brazilian and Portuguese stockholders. The
company controls the French company, Société Minière, associated with
the Welsbach Co.
As noted above, one French company has exploited monazite deposits in
the territory immediately behind the government lands in the State of
Rio de Janeiro. Another French company has worked the black sands along
the Parahyba River, near Sapucaica, which contain traces of monazite.
=India.=--Before the war, the German manufacturers of thorium nitrate
exercised as close control over the monazite deposits of Travancore,
India, as over those of Brazil. Only a limited quantity of the sand
was sold to gas-mantle manufacturers and other consumers in the United
Kingdom, and then at a price nine times the price paid by the German
consumers. Such a monoply of the supplies of raw material made the
German monoply of the thorium nitrate industry almost complete.
According to S. J. Johnstone, in an address at the annual meeting of
the Society of Chemical Industry in July, 1916, the Germans obtained
practical control of the Travancore monazite deposits in the following
manner: A lease for working these deposits was granted some years ago
by the Travancore Durbar, with the approval of the Government of India,
to the London Cosmopolitan Tin Mining Co., which contracted to sell the
whole of its output to a German firm. Soon after the outbreak of war
it was found that the whole of the preference shares and 11,000 of the
ordinary shares of the Travancore Minerals Co. were held in trust for
the Auer company, of Berlin.
The India Office decided that in the future all directors of the
company working the concession must be British-born and that the
company, must be ready at all times to sell monazite sand direct, and
at a fair price, to British firms. German contracts were canceled. A
second company, Thorium, Ltd., obtained a 20-year lease to work 150
acres in Travancore for monazite sand, and is exporting the sand and
manufacturing thorium nitrate from it at works in England. A great deal
of Travancore monazite has been imported by American companies.
POSITION OF THE UNITED STATES
As outlined above, it can be readily seen that the United States is
dependent upon Brazil and India for its raw materials, as domestic
deposits are not large enough to furnish the required supply and cannot
be worked in competition with the more cheaply mined foreign deposits.
The average concentrate obtained in the Carolinas runs about 3¹⁄₂ to
4 per cent. thorium oxide; that obtained in Brazil averages somewhat
over 8 per cent. Under such conditions it is difficult for the Carolina
monazite to compete with that from Brazil or from India. In addition,
a very considerable amount of the Carolina monazite available has been
removed. The old workings are more or less covered up and the whole
industry has become completely disorganized.
Whilst these deposits were being mined and operated farmers were in
the habit of making their own concentrate in crude sluice boxes.
The product thus obtained averaged about 35 per cent. monazite. The
concentrates were then sold to a refinery, where it was best treated by
electromagnetic separators, such as the Wetherill machine. The final
product obtained from these machines was ready for chemical treatment
for the extraction of the thorium.
Practically the same treatment is given to the monazite from Brazil
and India. As the concentrate obtained is of much higher grade, the
additional charges for freight and duty, which are not borne by the
Carolinas product, are more than offset. Undoubtedly, unless a very
high tariff is placed on the monazite from Brazil and India, our
future supplies will come from these two sources, at least for some
time. It is very doubtful whether with a high tariff the Carolina
deposits could furnish the monazite required in this country, even for
a few years, and under the most favorable conditions it would take some
time, possibly six months to a year, to revive the industry.
The Allies and practically the whole world are dependent upon the
United States for the manufactured products, thorium nitrate and gas
mantles. Whether this monoply will continue is doubtful, as there is
a movement in England to encourage both the thorium nitrate and the
gas-mantle industry.