The distribution of the 1915 product, by counties, was as follows: Alameda, Butte, San Luis Obispo, Santa Clara, Siskiyou, Totals *Combined to conceal output of a single producer in each. A larger amount than the above figures was shown in our Press Bulletin No. 35, issued April 28, 1916. Later information indicates that in one or two localities a considerable tonnage of chromite was actually mined in 1915, and included in the reports of production to this Bureau, though the major portion of it was not shipped from the property until after January 1, 1916. For this reason we have here included for 1915 only such material as was actually disposed of during that year. The annual output of chromite since 1887 has been as follows: Lime to the amount of 356,534 barrels, valued at $286,304, was produced from eight counties during 1915, as compared with 439,961 barrels, valued at $378,663, from ten counties in 1914. This figure includes only such lime as is used in building operations. That utilized in sugar making and as a fertilizer are classified under "in dustrial materials." That consumed in cement manufacture is included in the value of cement. Distribution, by counties, is shown in the following table: For table of production by years, see under "industrial" limestone. MAGNESITE. Bibliography: State Mineralogist Reports XII, XIII. Bulletin 38. Reports on Napa, Sonoma, Fresno, 1915. U. S. G. S. Bulletins, 355, 540. Magnesite has for a number of years been known to exist in many localities in California. In quality it is very high grade, many deposits yielding material carrying about 95% magnesium carbonate. The deposits are mostly in the metamorphic rocks of the Coast Range and Sierra Nevada Mountains, and are scattered over an area nearly four hundred miles long. One deposit of sedimentary origin is situated in the Mojave Desert region. California is the only state, so far of record, in the United States, having magnesite in commercial quantities. During the year 1915, there was considerable activity in the production of magnesite, giving an output nearly double that of the highest previous year (i. e., 1910). The curtailing of European imports due to the war, the lowering of transcontinental railroad rates on magnesite, manganese and chrome, and the added possibilities for transportation through the Panama Canal, to eastern markets, have led to the increased production. The permanent nature of improvements at some deposits gives promise that future production will be still greater. The photographs (pp. 48 and 49) illustrate the two types of furnaces used in calcining magnesite in California. Producing Districts. The following notes are here recorded concerning the principal producing districts of the state in 1915: The Tulare Mining Company, Tulare County, as for some years past, was the largest single producer. The magnesite is stoped in underground workings, and calcined in two vertical, shaft kilns. A railroad spur runs direct to the furnaces. The Porterville Magnesite Company is stoping and quarrying, shipping the product crude. Some output was made from leases operated by the California Magnesite Company. The Lindsay Mining Company has since built a railroad spur and for 1916 will show considerable shipments of crude. In Santa Clara County, at the Red Mountain deposit, the material is stoped underground, calcined in two vertical kilns, and transported 33 miles by auto trucks to the railroad at Livermore. The adjoining property of the Pacific Magnesite Company is being equipped. In the Sherlock mine, Madrone, the rock is quarried, and shipped crude. Shaft furnace of Western Magnesite Development Co., at Red Mountain, The Sonoma Magnesite Company, Sonoma County, is operating a rotary kiln, and has completed a short railroad for delivery to the main line. Shipments of both raw and calcined ore are made. In 1915, motor trucks were utilized. The Refractory Magnesite Company at Preston has a magnesite which burns brown, carrying up to 6% Fe2O3 and resembles the Austrian "spæder," particularly desired by the steel men. A considerable tonnage was shipped from the sedimentary deposit at Bissell, in Kern County, and calcined in two rotary kilns at Los Angeles before shipment east. In Napa County some ore was shipped, crude, from the White Rock mine in Pope Valley, and from a property of the Tulare Mining Company. There is a calcining plant in operation at San Diego burning magnesite from Lower California, Mexico. To date it has not treated any California magnesite. A number of owners have carried on development work, and it seems assured that a much greater demand can easily be met by the various California deposits. Uses. Rotary kiln of Sonoma Magnesite Co., at Magnesite, Sonoma County, California. The principal uses at the present time include: refractory linings for basic open-hearth steel furnaces, copper reverberatories and converters, bullion and other metallurgical furnaces; in the manufacture 2 * of paper from wood pulp; and in structural work, for flooring, wainscoting, tiling, sanitary kitchen and hospital finishing, etc. In connection with building work it has proven particularly efficient as a flooring for steel railroad coaches, on account of having greater elasticity and resilience than "Portland" cement. For refractory purposes, the magnesite is "dead-burned"-i. e., all or practically all of the CO, is expelled from it. For cement purposes, it is left "caustic❞— i. e., from 5% to 10% of CO, is retained. When dry caustic magnesite is mixed with a solution of magnesium chloride (MgCl2) in proper proportions, a very strong cement is produced, known as oxychloride or Sorel cement. "It is applied in a plastic form, which sets in a few hours as a tough, seamless surface. It has also a very strong bonding power, and will hold firmly to wood, metal, or concrete as a base. It may be finished with a very smooth, even surface, which will take a good wax or oil polish. As ordinarily mixed there is added a certain proportion of wood flour, cork, asbestos, or other filler, thereby adding to the elastic properties of the finished product." Its surface is described as "warm" and "quiet" as a result of the elastic and nonconducting character of the composite material. The cement is usually colored by the addition of some mineral pigment to the materials before mixing as cement. The desirable qualities of any flooring material (cost not considered) are listed for purposes of analysis or comparison under eighteen heads, as follows: Cleanliness (sanitary qualities), quietness, immunity from abrasion (surface wear), resilience, immunity from slipperiness, appearance, waterproof character, plasticity, warmth (thermal insulation), life (immunity from deterioration with age), acid-proof character, alkaliproof character, fire resistance, elasticity, crushing strength, structural strength (rupture), immunity from expansion and contraction, and lightness. The importance of these several qualities varies with the varying requirements to be met; for instance, in some places, as in hospitals, cleanliness is one of the prime considerations; in other places immunity from abrasion might be one of the principal requisites. As to most of these qualities the conclusion is reached that the magnesia cement affords one of the most satisfactory flooring materials for many purposes such as in kitchen, laundry, toilet, and bathrooms, corridors, large rooms or halls in public or other buildings, including hospitals, factories, shops and restaurants. There is no doubt that the material is steadily coming into more general recognition and favor for these uses. For a few special uses it is more or less disqualified; as an instance, it is not suited for con 8In this summary of the uses and properties of magnesia cement we have drawn freely from the following references: Eng. Soc. Western Pennsylvania Proc., 1913, vol. 29, pp. 305-338, 418-444; |