struction of swimming tanks or for conditions of permanent wetness, since under constant immersion it gradually softens, although it is said to withstand intermittent wetting and drying and is recommended for shower baths. Naturally it is not acid-proof and not wholly alkaliproof, which might be a disadvantage in use for laboratory floors and tables; but these are rather special requirements. Its cost per square foot is given as 25 to 33 cents, depending on area, which is estimated to be lower than marble, cork, rubber, clay or mosaic tile, slate, or terrazzo, although more expensive than wood, asphalt, linoleum, or Portland cement. In the discussion of the subject the causes of failure are ascribed to uncertain climatic changes, lack of uniformity in the mixtures used, lack of care on the part of those handling the materials, possible deterioration of materials used through exposure (either before or after mixing), lack of proper preparation of foundations on which the material is to be laid, and, as a very important factor, experience or nonexperience in the manipulation or actual laying and troweling of the material. Data concerning the percentages of magnesium chloride and of ground calcined magnesia and data concerning the character and quantity of filler and color added to the commercial preparations are naturally guarded as trade secrets by the firms already in the 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 very 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:" Mixtures for the underlying or coarser layer. 1. 15 parts magnesia. [Parts by weight.] 10 parts magnesium chloride solution, 20° Baumé. (Sets in 36 hours.) 'Scherer, Robert-Der Magnesit, sein Vorkommen, seine Gewinnung und technische Verwertung, pp. 216-217, A. Hartleben's Bibliothek, Wien und Leipzig, 1908. 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. 4 parts wood flour, impregnated with 4 parts Terpentinharzlösung. (Sets in 30 hours.) The magnesite used is, as explained, the fine ground calcined (not dead-burned) of certain specified kinds or place of derivation regularly sold for the 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. If 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. 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 the present activity was seldom handled on the market in the crude state. It is ordinarily calcined and ground before being considered marketable. The value of the calcined magnesite varies, the San Francisco price for 1915 ranging from $25 to $45 per ton, which figure includes about $1 per ton freight. From 2 to 2 tons of the crude material are mined to make one ton of the calcined. In previous reports the foregoing circumstances were used in calculating an arbitrary value for the crude material at the mine, there having been very little product shipped crude. On a similar basis, the value of the 1915 crude would have been approximately $16 per ton. On the contrary, however, considerable tonnages were in 1915 shipped in the crude state, contracted for at prices ranging from $7 to $11 per ton, f. o. b. rail points, or an average of about $9 per ton. Magnesite products have been found to be highly satisfactory and are growing in popularity, and the future for this industry appears to be bright. A large supply is already known to exist in California, and only a sufficient demand and cheaper transportation are lacking to make this an item of greater consequence in the mineral total of the state. Production of crude magnesite for 1915, by county, is given in the following table, with total crude value. Approximately 11,000 tons were shipped in the calcined form, representing about two-thirds of the total: *Combined to conceal output of a single producer in each. Annual production for California, amount and value, since 1887, is MARBLE. Bibliography: State Mineralogist Report XII. Bulletin 38. Marble is widely distributed in California; and in a considerable variety of colors and grain. During 1915, the production amounted to 22,186 cubic feet, valued at $41,518, from Inyo, San Bernardino, Siskiyou and Tuolumne counties. Included in the output of Siskiyou County is a small amount of rhodonite which was used for decorative purposes. The decrease in output of marble the past two years is doubtless a reflection of the laxity in building operations, which is shown by some of the other structural materials, also. It is also probably due in part to the fact that foreign, eastern and Alaskan marbles are landed here by water cheaper than much of our local stone can be put on the market, on account of our higher labor costs and transportation difficulties. Data on annual production since 1887, as compiled by the State Mining Bureau, follows. Previous to 1894 no records of amount were preserved: Bibliography: State Mineralogist Report XII. Bulletin 38. Onyx and travertine are known to exist in a number of places in California, but there has been no production reported since the year 1896. SANDSTONE. Bibliography: State Mineralogist Report XII. Bulletin 38. Report on Colusa, etc., counties, 1915. An unlimited amount of high grade sandstone is available in California, but the wide use of concrete in buildings of every character, as well as the popularity of a lighter colored building stone, has retarded this branch of the mineral industry very seriously during recent years. In 1915 five counties-Napa, San Mateo, Santa Barbara, Siskiyou, and Ventura-turned out 63,350 cubic feet, valued at $8,438, which is a considerable drop from the previous year. The main feature of the loss is the closing of the well known Colusa quarries, on account of the competition of lighter colored materials. Amount and value, as far as contained in the records of this Bureau, are presented herewith, with total value from 1887 to date: Serpentine has not been produced in California at any time, to a very large extent, owing to defects in the stone, most of which is not of good texture. The following table shows the amount and value of serpentine since 1895 as recorded by this Bureau: |