MANGANESE

INTRODUCTION

This bulletin is issued for the purpose of stimulating prospecting and development of possible sources of manganese in Nevada.

In the rush to do the big things in the war, some of the smaller, but no less vital, things are possibly overlooked. We do not realize the importance of the little that we can do. For example, the supplying of some of those rare or uncommon metals, which in ordinary times would not be necessary, at this time may become a vital factor for the successful conduct of the war. At this time, more than at any other time in our history, we need to develop our own natural resources and import nothing which can be produced from within our own borders. This will release for other service ships which are so much needed at this time. Production from our own resources, taken up as a war emergency measure, may develop new lines of industry for times after the war.

NEED OF MANGANESE

Manganese is one of these metals. It is absolutely essential for the production of high-grade steel. A recent statement of Secretary Franklin K. Lane of the Interior Department is to the effect that 50,000 tons of shipping is now necessary to supply the demands of the steel industry of this country with manganese, imported from Brazil, and that, could this shipping be released, it would be capable of carrying 300,000 tons of food and material annually to Europe.

MANGANESE DEPOSITS

Manganese ores occur in many parts of the United States, and in times past have been exploited to a certain extent. The deposits, however, are all small as compared with certain foreign ones and, due to several factors, have not been developed more extensively. Some of these limiting conditions have been: location of the markets in the East resulting in the need of paying high freight rates in comparison with the total value of the ore, uncertainty of payments after shipment, influence of the presence of certain impurities on the value of the ore, and high grade of ore demanded. These conditions have been greatly altered, due to the demand for manganese since the war started. We can group our manganese deposits in three general classes:

(1) High-grade manganese ore chiefly valuable for manganese; (2) Manganese silver ores; and

(3) Manganese iron ores.

Most of the deposits in the United States are secondary and have originated by the concentration of manganese originally occurring in some other form, more widely distributed in adjoining rocks. In general, the deposits are of comparatively slight depth, often consist of lenses and pockets of good ore, but widely scattered over considerable territory, and therefore require careful study to determine their possibilities.

MANGANESE IN NEVADA

Nevada has not been formerly looked on as a promising State for manganese, but some good though small deposits have been found. At Golconda we have examples of the first class of deposits. Some very good ore has been found. These deposits have been described briefly

by E. C. Harder.* They are believed to consist of deposits formed from waters issuing from surrounding sedimentary rocks, and occur interstratified with silicious and calcareous tufa in a bedded deposit. At Pioche we have examples of the third class of deposits. A recent estimate of the Geological Survey places the probable ore in two Pioche deposits at 550,000 tons and possible ore at 1,000,000 tons, carrying approximately 12% manganese, 34% iron, 13% silica, and less than 0.1% phosphorus. While this type of ore has up to the present time been used only to a limited extent, more use may be made of it in the near future.

In view of the fact that little attention has been paid to this metal in the past, the extent of the mineralized sections of the State, and its common association with silver deposits, it is not unlikely that there may be many good deposits found here in Nevada. Recently very encouraging reports have come of new discoveries in different parts of the State, especially from near Las Vegas, Ely, and Golconda. The latest reports from Las Vegas indicate there are being shipped 60 tons daily with hopes of increasing this soon to 200 tons. Reports from Ely state they are making daily shipments of 20 to 25 tons and with improved transportation can increase this amount. If shipments of 220 tons daily could be maintained, they would have considerable influence on the general situation. In round figures they would total 80,000 tons yearly, and, as the estimated amount imported last year has been placed at about 500,000 tons, it is readily seen what an appreciable effect the Nevada supply would have.

The Mackay School of Mines has recently received from a number of different localities in the State very good samples of manganese ore. Attention should be directed first to securing ores of shipping grade without preliminary treatment. Some concentrating tests have been made to improve the grade of some of the low-grade silica-bearing ores with promising results. The Mackay School of Mines proposes to make further tests on this type of ore during the summer.

MANGANESE MINERALS

While there are many manganese minerals, there are only a very few commercially valuable. A few simple tests will serve to identify them. The oxides all have a dark color and streak; when fused with borax give an amethystine-colored bead; when fused with soda and niter give a greenish-colored bead; treated with hydrochloric acid give off chlorine gas.

The following are the chief minerals with a brief description of each : Pyrolusite.

This mineral is sometimes called "black oxide of manganese." Its composition is manganese dioxide containing 63.2% metallic manganese. It is a soft black mineral having a metallic to dull luster; usually soft enough to soil the fingers; occurs massive, compact, stalactitic, and as crusts; its powder is black and its color black to steelgray; gives an amethystine-colored bead when fused with borax; is soluble in hydrochloric acid liberating chlorine. It occurs in this State in several localities: Las Vegas, Ely, Golconda, and near Schurz.

Psilomelane.

This mineral does not have a definite composition, but the content of

*See "References" at end of this pamphlet.

manganese is usually high, not, however, as high as pyrolusite. In color it resembles pyrolusite, but is very much harder, being 4 to 5, while pyrolusite is 1 to 2.5; it is never crystallized; occurs as a smooth black massive mineral; it is infusible; generally yields water in a closed tube; gives reactions with hydrochloric acid and borax similar to pyrolusite. It is usually associated with pyrolusite, and in this State with rhodonite, as at Golconda.

Braunite.

This mineral is a manganese oxide of the composition Mn,O; hardness of 6 to 6.5; submetallic luster; brownish-black to steel-gray color; gives reactions similar to pyrolusite with borax and hydrochloric acid. Manganite.

This mineral is a hydrated form of the oxide, containing, when pure, 62.4% manganese; occurs as long and short prismatic crystals; has submetallic luster; steel-gray to black color; reddish-brown to black streak; gives with borax and hydrochloride acid reactions similar to pyrolusite.

Rhodochrosite.

This mineral is a carbonate, containing, when pure, 61.7% manganese; color rose-pink to brownish-red and brown; occurs massive, compact, and granular; hardness, 3.5 to 4.5; is transparent to opaque; brittle is infusible, but changes dark-colored under the blowpipe; gives amethystine-colored bead with borax; is soluble in warm hydrochloric acid with effervescence; shows cleavage parallel to the rhombohedron. It is found in this State at Austin.

Rhodonite.

This mineral is the manganese silicate. The pure mineral would be of no value as a commercial ore, due to the presence of silica. It is generally rose-red to brownish-red in color; hardness, 5.5 to 6.5; gives an amethystine bead with borax. It is found in this State near Golconda.

Wad.

This mineral is a mixture of manganese oxides, together with the oxides of some other metals, notably copper, lead, and cobalt; color dark-brown or black; varies in hardness from 1 to 6; gives with fluxes the same reactions as pyrolusite and also often will give tests for lead, copper, and cobalt.

COMMERCIAL ORES

There are several factors which determine commercial or shipping ore. These factors are influenced by the use to which the ore is to be put. For example, a different grade is desired for use in making dry batteries than for making of ferromanganese for use in steel. Following are in general the limiting conditions which the manganese ore must fulfil for the steel industry:

1. The content in metallic manganese must run over 38%, and a higher unit-value is paid on ores as the content of manganese rises. It is preferred that the content of manganese run over 40%.

2. The silica content of the ore should run less than 8%, although ore containing as high as 12% will be accepted by some buyers and up to 15% by imposing certain penalties. These penalties are referred to

later in this report. Silica is objectionable, due to its tendency to produce a large volume of slag and also to carry manganese into the slag when smelted.

3. Phosphorus is not eliminated in smelting manganese ore, and is therefore limited to a very small amount in commercial ore. In general, the ore must contain less than 0.20% phosphorus.

4. Ore to be used in making ferromanganese must contain less than 8% iron. This is necessary in order to produce an alloy running 80% manganese. The lower the iron the more desirable the ore.

Some of the samples sent to the laboratory have shown on analysis up to 3% tungsten as the trioxide. Inquiry has been made regarding its possible influence on the value of the ore. With one exception, the replies indicate that, while it is not detrimental, neither is it thought that any return could be made for the contained tungsten. One dealer stated the tungsten would detract from the value of the ore for his purpose.

As some of the Nevada ore has shown sulphur in the form of both sodium and calcium sulphates, inquiry has been made as to the allowable amount of sulphur, and this has been fixed by one dealer at from 1 to 2% and the ore still be of value in steel manufacture.

CHEMICAL ORE

For use in making dry batteries, glass, and in the enameling industry the highest grade ore is required. It is then called "chemical ore. This type of ore commands a slightly higher price than "metallurgical ore." It must contain high manganese, preferably about 50% metallic manganese, less than 1% iron, and less than 0.01% copper. Some ore of this grade has been found in Nevada, but in general the western ores contain too much iron or copper for this classification.

MANGANESE IN STEEL

Manganese, to become useful for the steel industry, must first be produced in the form of an iron-manganese alloy. If this alloy contains. under 20% manganese, it is known as spiegeleisen; if it contains between 20 and 80%, it is known as ferromanganese. The higher grade alloy is demanded by the steel industry, and up to the present time the demand has been satisfied. In the attempt to use the manganese iron ores which occur in large amounts in this country, the lower grade alloy may come into more extended use.

Speigeleisen is usually produced by smelting a manganese iron ore in the blast furnace. Lime is the principal flux. Silica is objectionable, owing to its tendency to produce a large volume of slag and at the same time carry away with it large amounts of manganese. Ferromanganese is produced by smelting a high-grade manganese ore in the blast furnace or in the electric furnace.

Manganese is used in steel for the following reasons:

First-To neutralize the harmful effects of sulphur by the formation of the less harmful sulphide of manganese.

Second-To remove oxygen from the steel and prevent thereby the formation of blowholes.

Third-To produce the special alloy steel known as manganese steel, used for implements or parts of machinery subject to great wear, as crushing surfaces of ore-crushers, parts of plows, rails for curves on street railways where subject to heavy use, and burglar-proof safes.