barometers, thermometers, thermostats, gas governors, mercuryvapor lamps, batteries, cosmetics, silvering mirrors, boiler compounds, phthallic acid, vermilion, and dental amalgam. t is also used in preparing raw material by hatters and furriers, and in the amalgamation of gold and silver ores.

Military uses.-Its military uses include fulminates for detonating high explosives and fixed ammunition; for medical use in drugs (calomel, corrosive sublimate), and dental amalgam; antifouling paint for ships' bottoms; storage batteries, barometers, etc.

SUBSTITUTES.

An important factor affecting the post-war demand for quicksilver is the use of substitutes. Just prior to the war the detonator manufacturers were using substitutes for fulminate of mercury. These substitutes were obtained from Germany and the supply was cut off by the war. Now there are several detonators on the market that are composed of substitutes. The substitutes for fulminate are commercially important, in the opinion of American manufacturers of blasting caps. While substitutes will not replace fulminate entirely (as most of them require fulminate to explode them), they are expected to cut down the consumption of fulminate about 75 per cent.

Prior to the war substitutes for fulminate could be secured from Germany at a price equivalent to about $41 a flask for quicksilver. The American substitutes can not compete with pure fulminate at prices lower than $75 a flask for mercury, and even at $105 a flask many of them are little cheaper.

As to the reliability of the substitutes for fulminate, the most tangible evidence is that the ordnance department of no allied Government permitted their use in caps or detonators for war purposes. The use of substitutes is, therefore, confined to the manufacture of blasting caps for use in mining and excavation and in the making of sporting ammunition. A misfire in either of these commodities is not so vital. In blasting it is possible to use two caps. in every important shot, and 100 per cent detonation is practically certain when this is done.

There are comparatively few applications of mercury where a substitute is not possible, although the substitute is generally not so good and frequently not so cheap. Mercury can be done away with in making cosmetics, for which 300 flasks are used annually. A large part of the consumption in drugs and chemicals could be saved by

I Data largely from evidence of Leslie Oliver, of the California Cap. Co., and F. L. Ransome, of the U. S Geological Survey, before the U. S. Tariff Commission at the San Francisco conference, June 26, 1919 The composition of these substitutes is varied. Lead (or silver) azide is one of the most important. Chlorato-trimercuraldehyde, diazobenzene nitrate, nitrogen sulphide, basic mercuric nitromethane, sodium fulminate, and other compounds are also employed.

67940-21-c-25-2

eliminating certain preparations for which substitutes can be used. Most of the consumption for water-treating compounds and for vermilion could be saved if necessary.

COUNTRIES OF LARGEST PRODUCTION.

During 1904 and 1905 the United States led the world in production, but from 1906 to 1916 Spain was the leading producer, accounting. for about one-third of the total. Italy, Austria, and the United States made up the major part of the remaining two-thirds. In 1913, the last year before the war, Spain produced 36,619 flasks of 75 pounds; Italy, 29,513: Austria, 24,104; United States, 20,213; Mexico and other countries, 6,606. On the outbreak of the war Austrian supplies were at once commandeered by the Central Powers, and Spanish supplies, controlled mainly in London, were held for allied use. Under war conditions the relative importance of the different countries changed to some extent, as may be seen in the following table: World's production of quicksilver, 1908-1917, in flasks of 75 pounds.

[From Mineral Resources, 1917, U. S. Geological Survey.]

Spain.

Mexico and other

countries..

$4,000

Total.....

28,954 532, 129 29,300 9800 91, 100, $500

10 31, 382 10 40, 933 10 32, 892 10 43, 912 10 36, 921 10 36, 619 10 28,000 10 35, 925 10 23, 369 10 25, 133

25,880 24,500 4,500 24,500 $4,500 $4,000 24,000 $4,000 $4,000

97,612 108,676 104, 741 120, 773 120, 813 117,055 107,589 118, 212 118,030 122,592

Statistics not available; estimate based on oral information from Russian special commission to United States in 1917.

10 Estadística minera de España, Madrid.

DEPOSITS IN THE UNITED STATES.

The quicksilver deposits of the United States are found as fissure fillings, often regular and linked together to form stock works; in complex fracture zones; along bedding and joint planes; and disseminated through the country rock. Ore shoots are extremely irregular. Ore and gangue are found as fissure filling, cementing breccias, or impregnating and replacing the wall rock.

Quicksilver ores are found in many kinds of igneous, sedimentary, and metamorphic rocks of various ages. Deposits often follow lines of regional fissuring. The relation is noticeably frequent between

igneous activity and the deposition of quicksilver ores. A considerable number of deposits have proved to be very superficial, decreasing rapidly in size and value at depth.

It is said that the United States can furnish an adequate supply of quicksilver for years to come, provided prices are maintained. The rich ores, however, are practically exhausted and few mines have large reserves even of low-grade ore. The remarkable outstanding feature of the American quicksilver industry is the extreme low grade of the raw material utilized. Material carrying even less than one-quarter of 1 per cent mercury is successfully treated at certain properties; the average ore mined in the United States contains about 0.5 per cent.

DOMESTIC PRODUCTION.

Quantity. The domestic production of quicksilver in 1918 was 32,883 flasks of 75 pounds each. This quantity is almost twice the production in 1914. In 1876 the United States produced 75,000 flasks as much as the total production of all Europe. In 1914 it ranked fourth and its output was only one-sixth of the world production. The United States production in 1905 was 30,534 flasks. It declined fairly steadily until 1914, when only 16,548 flasks were produced. In 1919, 21,348 flasks were produced.

In 1918, 69 per cent of the United States production came from California. Texas and Nevada made up 28 per cent and the remaining 3 per cent was produced in Oregon and Idaho. The largest American producer is the New Idria mine in San Benito County, California, which furnishes about one-third or the entire output of the United States. The Chisos mine in Brewster County, Texas, is credited with the second largest production. In the third quarter of 1920, only 12 mines reported production to the Geological Survey; nine of these were in California, one in Nevada, and two in Texas. Production of quicksilver in United States, 1902-1919.1

Flasks contain 764 pounds in 1902, 1903, and 5 months, 1904; 75 pounds since June 1, 1904.

* Oregon and Utah combined, 1905-6.

Production of quicksilver in United States, 1902-1919—Continued.

Grade. The following table, prepared from figures furnished by the United States Geological Survey, clearly shows the general decline in metal content of the American ores:

1 Figures do not include tonnage of dump material treated or metal recovered from this source.

ORGANIZATION AND CAPITALIZATION.

About one-third of the domestic production is made by the New Idria Quicksilver Mining Co., capitalized at $500,000. The remainder comes from a large number of companies, many of which operate on a small scale. The reduction plant of the New Idria Co. was burned in June, 1920.

PROCESSES OF EXTRACTION.

Furnace treatment, without previous concentration, has always been the common method for recovering mercury from its ore. The

two essential features of this process are calcining (volatilization of the metal by heating) and condensation. Few other processes that promise success have been developed. Preliminary wet gravity concent ation has been tried, and under some circumstances has met with qualified success. As a rule, however, it has not equaled the results of efficient furnace treatment either in the matter of recovery or of low costs. Its only attractive fields are in the treatment of dump material, or, at established mines, for gaining temporary increase in capacity. Concentration by flotation has also been attempted, but is still in the experimental stage. Leaching with alkaline sulphides is a possibility, but is not practiced at any quicksilver mine.

Furnace methods.-The most important advance in quicksilver reduction in the United States was the development of the Scott furnace in 1875. This is a shaft type of furnace with a fire box at the bottom. The ore travels from top to bottom on tiles or shelves, which are set at an angle and staggered. About 24 hours are allowed for the ore to pass through the furnace.

The installation cost of a Scott furnace plant is high, being generally estimated at approximately $1,000 per ton-day. More modern condenser construction permits the reduction of this estimate to $750 per ton of daily capacity No device has yet proved so generally efficient in operation. Severe tests have shown that with careful supervision extractions of over 90 per cent can be obtained with this type of furnace, and this from ore carrying only 5 or 6 pounds of metal per ton. Average practice (1918) in California probably did not recover over 75 per cent.

Encouraged by favorable results achieved by producer-gas fuel, an Austrian plant (Idria) has erected a new Kroupa furnace (patented) which has proved a distinct step toward the bettering of quicksilver metallurgy. The fundamental idea of this furnace construction is to drive off the mercury from the ore between highly heated walls. This type of furnace has vertical parallel shafts separated by walls built of refractory masonry, which contain the heating flues.

Rotary furnaces,' which have lately been built at one or two plants, give thorough satisfaction, and for certain types of ore may even displace the standard Scott furnace. Cast-iron retorts of round or D-shaped section have a limited use at small high-grade properties or for the treatment of residues. In addition to these, many other furnaces, notably of the Herreshoff type, have been tried.

Condensation.-The object of condensers is to cool the furnace gases sufficiently to allow the vaporized mercury to condense and the

Cf. Rotary cement kilns.