The absence of quartz is very noticeable. It is almost never found in the andalusite proper but is confined to veins crossing the mass. Barite also has been noted a few times, one large right angled twin having been found. Lazurite also has been found, not in the andalusite but in veins of milky quartz adjacent to the mass. It is of interest to note that Knopf points out that the occurrence examined by him across the canyon and to the southwest was first staked as a silver mine, the bright blue lazurite being thought to be AgBr. After assay showed no silver the claim was dropped. Later the brown andalusite mass was staked again, this time under the impression that it was apatite. This in turn proved valueless and was relinquished. USE. This deposit of andalusite serves as an extremely good example of a comparatively useless, rare, or 'museum' mineral first becoming common enough to be available on a commercial scale, because it has heretofore been observed only in small scattered masses or crystals, and second, at the same time finding a commercial use, until at present about 70 tons per week are being mined. Both of these have been the result of patience and thorough scientific research. For some years the manufacture of the porcelain core of the most modern type of automobile spark plug has tended toward the formation during the burning process of an increasingly higher content of a crystalline compound, thought to be an artificial sillimanite.' Bowen1 has recently shown, however, that in artificial melts of ALO, and Si0, in varying proportions the compound Al,O.SiO, corresponding to natural sillimanite does not form as has been stated in the earlier work on the subject but that the compound formed has a composition 3ALO2SiO. Not only is this compound similar chemically to sillimanite but its physical and optical properties are remarkably similar as well.2 This 'artificial sillimanite' produced in ceramic ware results from the molecular changes taking place in clay under the influence of heat and various fluxes. The highest content of 'sillimanite' has been accomplished by introducing into the unburned body artificially prepared 'sillimanite' in the form of a calcine-a mixture of clay, alumina, and fluxes, heated to a high temperature of about 1500° C. This was of course an expensive method to obtain the desired end although it has been used for several years in the manufacture of spark plugs. In order to eliminate the necessity of making an 'artificial sillimanite', the natural way out was to turn to one of the natural Al,SiO, compounds, namely, sillimanite, andalusite, or cyanite, but here the difficulty of obtaining any of these in sufficiently large quantities and in a pure state presented itself until the California andalusite deposit was located. 1 N. L. Bowen and J. W. Greig, J. Am. Cer. Soc., 7, 238-54 (1924). 2 In the original manuscript of the present paper the writer regarded the crystalline compound formed by the inversion of andalusite and cyanite and the crystals formed in porcelain as sillimanite, following the earlier work of the Geophysical Laboratory on the system Al-O.SiO2. Since the announcement of the work of Bowen and Greig it has been necessary in several cases to change 'sillimanite' to the new compound BALO.2SiO2.' This statement is made so that full credit may be given to them for the facts they have discovered and the writer's sincere thanks are due Dr. Bowen for his kindness in allowing this use of his manuscript before its actual publication, Careful research was then able to substitute this natural material for the artificial sillimanite' with the result that not only was the manufacture less expensive but also that resulting article was better than the previous one. Thermal Changes. Although the material is introduced into the clay body of the unburned porcelain core as andalusite, certain changes take place during the burning process and as a result of these there is present no andalusite in the finished article but all of the andalusite undergoes a molecular change to a compound of the composition 3A1,0,.2SiO, with excess of a glass highly siliceous in composition. This change is quite definite, taking place sharply and at a definite temperature. Under manufacturing conditions this temperature is in the neighborhood of cone 13 on the Seger scale (theoretically equal to 1390° C but actually probably considerably lower). Of interest from the microscopic standpoint is the behavior of andalusite during this change. Up to the inversion point andalusite retains all of its original optical properties except for the formation of small glass-like inclusions which apparently represent the fusion of included impurities. At the inversion point the clear homogeneous grains of andalusite give way to grains composed of fibrous or columnar crystals, each crystal parallel to the adjacent one with a narrow strip of glass between. The result is instead of a clear grain, a grain composed of a group of parallel crystals having all of the optical properties of 3A10.2SiO2, with glass between each. Traces of the remains of such structures can sometimes be seen in a section of a finished spark plug core. Cyanite also changes to 3A1,0,.2SiO, and glass under heat but at a lower temperature of about cone 11 (theoretically 1350° C). The structure developed is also different from that shown by the change in andalusite. Cyanite yields a body consisting of groups of interlocking fibers of 3A1,0,.2SiO, which are not parallel over any considerable length. Along with these are areas of glassy matter, generally more abundant than in the andalusite and due no doubt to the fact that cyanite is less pure as a rule than andalusite. Cyanite has higher specific gravity therefore more substance per unit volume, which when breaking up would yield more matter from each previous unit but should this change the relative amounts? The fact that andalusite changes to 3A1,0,.2SiO, at a temperature considerably below the final temperature to which the porecelain is burned has a very practical value because in this change from andalusite to 3A1,0.2SiO, and excess siliceous glass there is an increase in specific gravity and a consequent decrease in volume. This volume change tends to produce strains in the porcelain, which can be absorbed if the inversion takes place well below the final burning temperature. If this were not true and the change took place near the final temperature, the decidedly weaker porcelain might result. Incidentally, during this inversion the andalusite does not outwardly break down and lose its original form, so that good artificial pseud The statements made here are purely provisional. Investigation of the changes with temperature is to be made in more detail at a later date. omorphs of this mixture of 3A1,0,.2SiO, and glass after andalusite is readily obtained by simply heating for a sufficiently long period above the inversion temperature. This can not be done with eyanite because the expansion at the inversion point is so great that the cyanite breaks down into a chalky friable mass. The writer here wishes to acknowledge his sincere thanks to Dr. J. A. Jeffery, president, and Mr. F. H. Riddle, research director of the Champion Porcelain Company, whose interest and cooperation have made this note possible. NOTE. The foregoing paper was received through the courtesy of Dr. Joseph A. Jeffery, president of the Champion Porcelain Company, and published by permission of Professor Peck. Dr. Jeffery adds, in his letter accompanying: "It just occurred to me that you might be interested in knowing that the pyrophyllite possesses very valuable properties which aid us very greatly in the processing of the material through the plant. It is not only valuable in the wet-grinding process, but also greatly assists in maintaining a uniform moisture content during the working and pugging operations."-EDITOR. Personnel. ADMINISTRATIVE DIVISION. WALTER W. BRADLEY, Deputy State Mineralogist. The State Mining Bureau and particularly the Petroleum and Gas Department has been signally honored in the appointment of Mr. R. D. Bush, state oil and gas supervisor, by the President of the United States, to be a member of a commission of three to study and report on the Naval Oil Reserves and the leases thereon. The appointment will not require Mr. Bush to sever his connections with the State Mining Bureau. New Publications. During the period covered by this issue (January 15th to April 15th) the following Bureau publications have been made available for distribution: Mining in California (quarterly), January 1924, being Chapter No. 1, of State Commercial Mineral Notes: Nos. 10, 11, 12, January-March, inclusive. These 'notes' carry the lists of 'mineral deposits wanted' and 'minerals for sale,' issued in the form of a mimeographed sheet, monthly. It is mailed free of charge to those on the mailing list for Mining in California.' Owing to the very considerable increase in our mailing list for 'Mining in California,' which had grown beyond the ability of the present funds of the State Mining Bureau to pay the printing bills without additional revenue, it became necessary to place a subscription price on this quarterly of 25 cents per issue, or $1 per year paid in advance. Mail and Files. The Bureau maintains, in addition to its correspondence file, a mine report file which includes reports on some 7500 mines and mineral properties in California. Also there is available to the public a file of the permits granted to mining and oil corporations by the State Commissioner of Corporations. During the period of January 15-April 15, there were 2091 letters received and answered at the San Francisco office alone, covering a wide range of subjects concerning prospecting, mining and developing mineral products, reduction problems, and marketing of refined. products. DIVISION OF MINERALS AND STATISTICS. Statistics, Museum, Laboratory. WALTER W. BRADLEY, Deputy State Mineralogist. STATISTICS. California continues to produce commercially, as for a number of years past, at least fifty different mineral substances, the total annual value of which has averaged over $250,000,000 the last four years. The estimated value for 1923, as shown in the January issue of 'Mining in California' (see page 50 ante), was $270,472,000. At the present writing (April 15), reports are in hand from most of the producers. Data for several substances are now complete and have been compiled, being presented herewith. The data at hand indicate that there was no production in California in 1923 of the following substances, which have at one time or another in the past been on the active list here: Antimony, bismuth, cadmium, fluorspar, graphite, lithia, mica, molybdenum, serpentine, slate, strontium, and tin. In addition to the above, there are potential deposits of ores of the following which have not as yet yielded a commercial output: aluminum, arsenic, cobalt, nickel, nitrates, and vanadium. BARYTES. The output of crude barytes in California during 1923 amounted to a total of 2925 tons valued at $16,058 f. o. b. rail-shipping point, as compared with 3370 tons valued at $18,925 in 1922. The 1923 product came mainly from Nevada County, with smaller amounts from Mariposa and Shasta counties, and was consumed principally in the manufacture of lithopone. More than half of the total tonnage of barytes utilized in the United States is taken in the manufacture of lithopone, which is a chemically-prepared, white pigment containing approximately 70 per cent barium sulphate and 30 per cent zinc sulphide. This is one of the principal constituents of 'flat' wall paints. Total Barytes Production of California. The first recorded production of barytes in California, according to the statistical reports of the State Mining Bureau, was in 1910. The annual figures are as follows: Small amounts of bituminous rock are still occasionally used for road dressing in those districts adjacent to available deposits, though the |