business. The examination and standardization of the raw materials used, and of acceptable filler materials, and the establishment of standard proportions for the mixtures would seem to be about the only satisfactory way of attacking the problem.

The condition of the calcination of magnesite for cement uses is important, as the same material may undoubtedly be greatly varied in its reacting properties by differing treatment in the kiln. It is generally agreed that the magnesite for cement use must be comparatively free from lime, as lime has a greater tendency to reabsorb water and carbon dioxide than the magnesia, thereby causing swelling, and is therefore not so permanent in the completed cement as a pure magnesia material. The fillers used may constitute 10% to 40% of the whole cement, and commonly consist of ground marble, sand, sawdust, cork, asbestos or other materials. As an example of the formulas used in mixing such cements the following are quoted :1

10 parts asbestos powder.

5 parts wood flour.

1 part red ocher.

(Sets in 24 hours.)

2. 25 parts magnesia.

25 parts magnesium chloride, 21° Baumé.

44 parts wood flour, impregnated with 4 parts Terpentinharzlösung.
15 parts yellow ocher.

(Sets in 30 hours.)

The magnesite used is the fine-ground calcined (not dead-burned) of certain specified kinds or place of derivation regularly sold for plastic purposes. This material commonly comes in paper-lined casks, barrels or boxes, in which form it is fairly permanent, but it deteriorates by exposure, absorbing carbonic acid and moisture from the air.

Scherer, Robert-Der Magnesit, sein Vorkommen, seine Gewinnung und technische Verwertung, pp. 216-217, A. Hartleben's Bibliothek, Wien und Leipzig, 1908.

carefully handled it can probably be kept unopened a year or more, but it should be used within a few weeks after being opened, even under most favorable conditions.

The use of magnesia cement has been suggested as a protecting coating for mine timbers, particularly against the fire hazard. The necessary qualities for any substance for such purpose have been summarized as follows: It should be resistant to abrasion, and to impact and structural stresses. It should be durable when subjected to the action of the elements, and stable to any minor derangements of the base on which it is placed. It must be relatively unaffected by changes in temperature, by the action of water, and should adhere to the material on which it is placed, and it should also be free from shrinkage cracks due to setting up the material, and have the ability to resist fire. Magnesite cement appears to fulfill the various conditions thus outlined.

It is stated that some metallic magnesium has been prepared electrolytically at Niagara Falls from magnesite.

For refractory purposes the calcined magnesite is largely made up into bricks, similar to fire-brick for furnace linings. It is also used un-consolidated, as 'grain' magnesite. For such, an iron content is desirable, as it allows of a slight sintering in forming the brick. Deadburned, pure, magnesia can not be sintered except at very high temperatures; and it has little or no plasticity, so that it is hard to handle. Its plasticity is said to be improved by using with it some partly calcined or caustic magnesite. Heavy pressure will bind the material sufficiently to allow it to be sintered.

A coating of crushed magnesite is laid on hearths used for heating steel stock for rolling, to prevent the scale formed from attacking the fire-brick of the hearth.

Imports and Domestic Production.

Reports of the U. S. Bureau of Foreign and Domestic Commerce show imports of calcined magnesite to have been 172,591 long tons in 1913; 144,747 in 1914, and 63,347 in 1915; most of it coming from Austria-Hungary and some from Greece. For the same years the production of crude (from 2 to 2 tons of crude ore required to yield one ton of the calcined) magnesite in California (the sole producer of those years, in the United States) was: 9632 short tons, 11,438 tons, 30,721 tons, respectively. For 1916 the California output leaped to 154,052 tons of crude and to 209,648 tons in 1917, but has dropped considerably since then on account of resumption of foreign importations, which totaled 52,483 long tons in 1921, valued at $776,384, being then admitted duty free. Shipments from Washington were begun late in 1916; and during the following three years assumed important proportions, but only a small tonnage was shipped in 1922.

The Tariff Act of 1922, which became effective September 22nd, last year, placed the following import duties on magnesite: Crude magnesite, per lb.; caustic-calcined magnesite e per lb.; dead-burned and grain magnesite, not suitable for manufacture into oxychloride cements, 23/40¢ per lb.; magnesite brick, 3¢ per lb. and 10% ad valorem. The figures of imports for 1922 after that date have not yet been published

by the U. S. Bureau of Foreign and Domestic Commerce, but for the nearly 10 months up to that time, the total was 112,159 long tons valued at $1,757,636, as compared with the figures shown in the preceding paragraph.

Output and Value.

In considering mineral production, the value of the crude material is used as far as practicable. Magnesite presents a peculiar example of a material which previous to 1916 was seldom handled on the market in the crude state. It is mainly calcined and ground before being considered marketable. From 2 to 24 tons of crude material are mined to make one ton of the calcined. In the earlier reports an arbitrary value for the crude material at the mine was calculated from the above on the basis of the calcined value, there having been very little product shipped crude. On the contrary, however, considerable tonnages since 1916 have been shipped in the crude state, contracted for at prices ranging from $7 to $17 per ton, f. o. b. rail points. The average was $10.50 per ton, for 1922. This is the basis of the valuation used herein.

The production of crude magnesite in California during the year 1922 totaled 55,637 tons, valued at $594,665 f. o. b. rail-shipping point. This is an increase over the 47,837 tons and $511,102 in 1921.

The main hope for the future for California magnesite appears to be in the development of the plastic business, particularly in the territory west of the Rocky Mountains; and in the manufacture of refractory brick to be utilized mainly by the copper and lead smelters in the same district. It is possible that California magnesite may be sent via the Panama canal to the Atlantic seaboard; but, on account of our higher production costs, it is difficult to see how we can compete with the Grecian article at Atlantic ports.

Several plants are reported making refractory brick here from California magnesite. The ore from the White Rock Mine in Napa County, and that from the old Kolling (Refractory Magnesite Company) Mine, Sonoma County, is a natural ferro-magnesite and has found a ready market for refractory purposes.

In 1918, for the first time since Tulare County became an important producer of this mineral, it was surpassed in tonnage output for the year, but regained the lead in 1919, followed by Santa Clara and Napa counties, respectively. The same ranking was retained in 1920; but Santa Clara took the lead in 1921. The largest individual producer in 1920-1922 has been the Western Magnesite Development Co., in Santa Clara County, operated under lease by C. S. Maltby. A total of 24,091 tons was reported as shipped calcined by Californian mines in 1922, representing anoroximately 52,205 tons of crude ore.

Owing to increased building operations, and the duty on foreign importations, the outlook for magnesite is improving. Research work is being conducted by the larger operators to insure uniformity of product, and to work out formulae and mixtures for its application in the plastic trade. Present quotations (March) are reported at $14 per ton crude, f. o. b. California points, and $40 per ton calcined,

Production of crude magnesite for 1922, by counties, is given in the following table, with total crude value:

Santa Clara

Stanislaus

Tulare

County

Fresno, Napa, San Benito, Tuolumne*.

Totals.

*Combined to conceal output of a single operator in each.

Total Magnesite Production of California.

The first commercial production of magnesite in California was made in the latter part of 1886 from the Cedar Mountain district,' southeast of Livermore, Alameda County. Shipments amounting to 'several tons' or 'several carloads' were sent by rail to New York; but there is apparently no exact record of the amount for that first year. The statistical records of the State Mining Bureau began with the year 1887, and the table herewith shows the figures for amount and value, annually, from that time. Shipments of magnesite from Napa County began in 1891 from the Snowflake Mine; from the Red Mountain deposits in Santa Clara County, in 1899; and from Tulare County in 1900. Production of Magnesite In California, Since 1887.

'See U. S. Geol. Surv.; Mineral Resources of U. S., 1886, pp. 6 and 696.

Totals..

MICA.

Bibliography: State Mineralogist Reports II, IV. Bulletins 38. 67. No commercial production of mica has recently been reported in California. Production in previous years has been as follows:

"The different uses to which mica is put depend on its form-whether in sheets or in powder. Sheet mica is used in the electrical industry for glazing, and to some extent for other purposes. Ground mica is used chiefly in the decorative trades and in insulation. "Sheet mica finds its greatest use in the electrical industry, where an insulating, noninflammable material is necessary. It is used in sheets and as washers and disks in dynamo-electric machinery, electric-light sockets, spark plugs, insulators, guards in rheostats, fuse boxes, and telephones. Flexible cloth and tape, covered with mica. find varied uses in electrical apparatus. Sheet mica is used for glazing the fronts of stoves and for making lamp chimneys and lamp shades. It is also used in spectacles, automobile shields, phonograph diaphragms, in windows where glass would be broken and in lantern transparencies.

"Ground mica is used for decoration in wall paper, to which it gives luster and brightness; in fancy paints, ornamental tiles, concrete, rubber goods, pipe and boiler Coverings, insulating compounds, fireproof paints and coverings, patent roofing material, molded mica (ground mica mixed with shellac), and calico printing; as absorbent for nitroglycerin in the manufacture of 'mica powder,' in tempering steel; to a large extent as a lubricant for wooden bearings, or, mixed with oil, as a lubricant for metal bearings; and as a filler for various products. Tar and other roofing papers are coated with coarsely ground mica to prevent sticking when they are rolled for shipment. A possible value of ground mica as a chemical source of potash salts is indicated in a recent Geological survey report.2

"It is understood that sheet mica has come to be of importance as a war mineral through its use abroad as windows in masks worn for defense against asphyxiating gases, and for other uses where a transparent, noninflammable, nonshattering material is necessary, as in automobile goggles and in windows for armored cars."

Present New York quotations for No. 1 quality sheet mica are from 15e per lb. for 14x2 inch to $3.60 per lb. for 6x6 inch, f. o. b. North Carolina, thumb trimmed; punch 8c, other grades, 25c to $3.25 according to size; flake 12c per lb.; scrap $25 per ton; f. o. b. Virginia points.

MOLYBDENUM.

Bibliography: Reports XIV, XVII. Bulletin 67. U. S. Bur. of Min., Bulletin 111. Proc. Colo. Sci. Soc., Vol. XI.

Molybdenum is used as an alloy constituent in the steel industry, and in certain forms of electrical apparatus. Included in the latter, is its successful substitution for platinum and platinum-iridium in electric contact-making and breaking devices. In alloys it is used similarly to and in conjunction with chromium, cobalt, iron, manganese, nickel, tungsten, and vanadium. The oxides and the ammonium salt have important chemical uses.

The two principal molybdenum minerals are: the sulphide, molybdenite; and wulfenite, lead molybdate; the former furnishing practically the entire commercial output. Molybdenite is found in or associated with acidic igneous rocks, such as granite and pegmatite. The chief commercial sources have been New South Wales, Queensland, and Norway, with some also from Canada.

Schaller. W. T., Mica in 1916; U. S. Geol. Surv.. Min. Res. of U. S. 1916, p. 304, 1917. Butler. B. S., Potash in certain copper and gold ores, with a note on muscovite by George Steiger; U. S. Geol. Survey Bull. 620, pp. 227-235, 1916.