Coal investigations have taken the form of the possible utilization of California lignite in the production of pig-iron and steel in the electric furnace under the Driscoll patents. This is a process in which the volatile gases are driven from the coal and used in a gas engine to generate the required electric current. The carbon remaining is utilized to reduce the iron ore to metallic iron (sponge iron), which is then melted in the electric arc. The apparatus comprises a combination rotary kiln and electric furnace and the process is continuous. Small scale tests have shown California lignite to be suitable for this process. Others have investigated the low-temperature distillation of the lignite under a German patented process with the production of a semi-coke briquette, said to be an ideal smokeless domestic fuel, and other by-products. Still other investigators are figuring on the manufacture of calcium carbide (CaC2) from lime and lignite coal. Apparently, the time is not far distant when the coal deposits of California will be developed to a much greater extent than at present; the better grades being used for domestic and steam fuel, in competition with imported coal, and the lower grades as powdered coal, in the manufacture of producer gas, or in one or more of the other industrial processes outlined above.

The demand for building materials continued active during 1923 and the established cement plants in this district, one each in Contra Costa, Solano, Santa Cruz and San Benito counties, enjoyed a prosperous year. Pacific Portland Cement Company started the construction of a 2000 barrel per day unit of a new cement plant, located on San Francisco Bay near Redwood City, approximately at the site of the construction and launching during the war of the concrete ship, Faith.

The wet process of manufacture will be used. Two of the principal raw materials, oyster and claim shells, and clay, will be obtained from the bay bottom by a suction dredger, and conveyed to the plant. These shell deposits are said to be practically inexhaustible. The plant is expected to be completed by July of this year. Its location gives it the advantage of direct water and rail shipment for the finished product, while at the same time the principal aw materials are at hand. It is reported that the Guadalupe Portland Cement Company expects to build a plant six miles southwest of San Jose, which will have an initial capacity of 2500 barrels per day. An immense hill of limestone is said to have been acquired in the vicinity of the proposed plant.

Yosemite Portland Cement Co. began construction of a large cement plant at Merced. Limestone occurring near El Portal will be utilized.

MAGNESITE.

Magnesite production, which is confined almost entirely to the San Francisco field division, showed a healthy growth during 1923. Several old properties were re-opened and one new deposit was worked.

The following data on the active magnesite properties in the district were prepared by Mr. Walter W. Bradley, deputy State Mineralogist, as the result of a short field trip.

Napa County.

Maltby No. 2 Magnesite Mine, C. S. Maltby, Humboldt Bank Bldg., San Francisco, lessee. The lease covers the old Blanco and the Snowflake mines, owned by the Tulare Mining Company, the first-named

having been operated by that company during 1917 and 1918. They were among the first magnesite mines to be worked in California, shipments having begun in 1891 and continuing for ten years at a rate of over 1000 tons per year. They are in Sec. 28, T. 8 N., R. 4 W., M. D. M. about two miles south of the old Chiles mill in Chiles Valley.

Since taking over this property in February 1923, the present lessee has driven a new adit in the Blanco ground 1000' long which crosscuts the vein at 78' on the dip (or 53' vertical) lower than the bottom level of the former operators. Drifts have been run 100' north and 165' south, the vein showing an average of 6' in width. The ore is being broken down by overhand stoping, and the small proportion of waste is sorted in the stopes, by forks and by hand.

Calcining equipment consists (see photo) of a rotary kiln, 31' inside diameter, by 50' long, driven by a 6 h.p. gas engine and oil fired. The

Calcining plant at Maltby No. 2 Magnesite Mine, Chiles Valley, Napa County, California. Producing dead-burned magnesite in a rotary kiln. Photo by Walter W. Bradley.

ore is crushed to pass 1-inch mesh before charging to the furnace, and is dead-burned for refractory purposes. The output of the furnace is 15 tons of calcined material per 24 hours. This rotary kiln was formerly in use for quicksilver reduction at the Bella Union quicksilver mine near Oakville in the same county. The calcines as discharged from the furnace are raised by a bucket elevator and run over a sheetiron chute to the bunker, from which the motor trucks are loaded which haul the product to the railroad at Rutherford. Maltby states that he is having a ready sale, mainly on the Pacific Coast, for the deadburned magnesite which he is producing here and at the Sampson mine in San Benito County, which he is also operating.

The White Rock magnesite mine in Pope Valley, operated by C. S. Maltby of San Francisco under lease during 1921-1922 was closed

down early in 1923 and the movable equipment transferred to the Blanco mine in Chiles Valley. It is stated that the orebodies of the White Rock were bottomed at a depth of 300 feet below the outcrop.

San Benito County.

The Sampson Magnesite Mine (known also as Maltby No. 3), west of Idria, is being operated under lease by C. S. Maltby, Humboldt Bank Bldg., San Francisco. The six vertical kilns formerly in use at this mine have been replaced by a rotary furnace 7' by 80' (see photo), operating at 1 minutes per revolution. It is oil-fired and is producing 35 tons of dead-burned magnesite per 24 hours. The ore is crushed to 3-inch mesh before charging, and 23 tons of crude ore are required

Calcining plant at the Sampson Magnesite Mine, west of Idria, San Benito County, California. Producing dead-burned magnesite in a rotary kiln. Photo by Walter W. Bradley.

for 1 ton of calcined. Steam power is used. Fuel oil is obtained from the pipe line of the Associated Oil Company at Mendota, there being a pumping station on the line at that point. The calcined ore is hauled by trucks to the railroad at Mendota.

As the orebody is on top of a ridge, the ore is broken by quarrying operations, and carried to the furnace by a Painter aerial tram, 5000 feet in length, having 16 buckets and being gravity operated. Jackhammer drills are used in the quarry. The compressor is driven by a 4-cylinder gasoline engine which formerly did duty in a Packard automobile. At the time of our visit (in November, last) it was certainly shooting merrily along on all four with a sharp bark out there on the open hillside without any muffler to worry it.

Santa Clara County.

The Western Magnesite Company's properties (known also as Maltby No. 1 Mine) 33 miles southeast of Livermore have been operated under lease by C. S. Maltby, Humboldt Bank Bldg., San Francisco, since 1919. Many improvements have been made in the plant equipment, and new orebodies have been developed. The earlier underground operations were due east from the furnaces, and some ore is still being drawn from that portion of the property. Later developments have been towards the north and northwest from the older workings. While none

of the north-end stopes have as yet reached the size of some of the older south-end orebodies (there was one, 300' long x 50' wide x 300' high;

Tramming ore from north end workings at Maltby No. 1 Mine (Western Magnesite Development Co.), on Red Mountain, Santa Clara County, Cal. Photo by Walter W. Bradley.

and another 200' long x 150' high x 30' wide), some are over 20' wide in places. The ore is of the same, white, high-grade character.

Öre from the north end is trammed around the hill (see photo) to the loading bunkers of the main aerial tram (of which there were two). When visited in November 1923, preparations were being made for the installation of a third aerial tramway, at the north end, in order to eliminate the long haul around the hill. A total of 150-200 tons of ore per day was being delivered to the furnaces, of which 40 tons was being mined at the south end, 30 tons from the extreme north end, and the balance from the main north workings. A new 4-inch pipe line was being laid direct to the north end to serve those workings with compressed air, in place of the line from the south end around the hill.

Pressure is maintained at 100 pounds at the compressors (two 50 h.p. Chicago Pneumatic, direct-connected to oil engines; also a Doak compressor as extra stand-by) and at least 90 pounds at the mine.

There are four upright kilns which burn the lump ore, and a Scott fine-ore quicksilver furnace which handles the fines. The ore as it comes from the mine is dumped on grizzlies set with a 1 inch opening; and the through material passed over a 3-inch screen. The plus 3-inch material goes to the Scott, and the minus 3-inch to the waste dump as it contains mostly impurities. There is a Thwing electric pyrometer on the Scott furnace, by which the temperature is maintained at 2100° F. The calcines are drawn each hour, and an output of 20-24 tons per day obtained. The upright kilns are drawn every 2 hours, and their output totals 50 tons daily for the four. The burned lump. ore is carried by a belt conveyor to a trommel with 1-inch apertures. The waste and off-colored magnesite are picked off the belt. The unburned cores after passing out of the trommel are hauled back to the main ore bin and re-burned in the kilns. Steam for atomizing the fuel oil is provided by two boilers, of 100 h.p. respectively. There were 14 motor trucks in service, hauling the calcined magnesite to the railroad at Livermore.

Tulare County.

Magnesite mining in Tulare County at the present time is practically confined to the several properties operated by the Sierra Magnesite Company, and to the Hoff-Harker lease on the old Harker or Porterville Hill mine.

Harker Mine. This property is owned by Mrs. Barngrover, Porterville, widow of Chas. S. Harker, and is at present under lease to Hoff & Harker. From 1915 to 1921 it was operated by the Porterville Magnesite Company and a large tonnage of ore mined, a part of which was calcined before shipping. It is two miles from the railroad at Porterville. During 1922 the property was operated under lease by the Sierra Magnesite Company, the ore being calcined in their furnaces at Porterville.

When visited in November, 1923, the rotary kiln was not in use, the present lessees confining their work to a vertical kiln of 15 tons calcined daily capacity. The product is shipped for plastic purposes. There is a small crushing plant, the equipment of which includes a hammer mill and a buhr mill for grinding the calcined material, although not being utilized at the time. The ore is being mined from the veins on the north side of Porterville Hill and hauled by motor trucks around to the furnace, which is on the south side of the hill.

Sierra Magnesite Company. This company was organized in 1920, and took over all of the important producing properties in the vicinity of Porterville, which they still retain with the exception of the Harker Mine (Porterville Magnesite Company) which, however, they operated during 1922. The Sierra company now owns in fee the properties described in preceding reports of the State Mineralogist1 under the following names: Rex Plaster Company, Lindsay Mining Company, Tulare Mining Company, and mineral rights of the Oakland Magnesite

1 1 Report XV, pp. 919-940, 1917; Report XVIII, pp. 528-535, 1922.