A SUCCESSFUL baryles-minning enterprise operates about a mile west of El Portal, on the Merced River in Mariposa County, Calif. Barite was first discovered and mined in the region in the 'eighties, (1880) on the north side of the river. Later, El Portal Mining Company and Western Rock Products Company exploited the deposit. Subsequently the Yosemite Barium Company acquired the property, and in 1927 opened up a series of lenses south of the river. The barite was marketed in crude form, and about 75 tons per day was shipped, being hauled by motor truck to El Portal. Later the National Pigments Company acquired the property.

The barite deposits, in the form of irregular lenses in schists and slates, appear to be part of the Calaveras formation, a wide zone of metamorphics of Carboniferous age, intruded by granites and granodiorites. The area is near El Portal and extends to the upper high country beyond Yosemite Valley. Elevation of the deposit near the river is 2,000 ft., but south the elevations rapidly increase. About five mile south of the river, at an elevation of 5,000 ft., according to reports of the State Mineralogist, more barite has been discovered and some work done.

The property of the National Pigments Company is accessible to railroad transportation, as the Yosemite Valley Railroad extends on the north side of the Merced River, and a spur has been built to the new treatment plant, which has been in operation for about two months. A barite lens about 150 ft. maximum width and about 1,000 ft. in length, south of the river and several hundred feet above it, is being mined by quarry and glory-hole methods. The crushed product is transported to the plant on the north side of the river by a Leschen wire-rope tram 3,400 ft. in length. Raw material is crushed to 1 1/8 in. maximum size. A motor is used on the tramway for starting and also for controlling speed. A 610-cu.ft. Ingersoll-Rand compressor supplies the quarry and a Sullivan drill sharpener is used for sharpening steel. A 35-hp, single-drum hoist served an incline up which men and supplies are transported from the highway to the quarry.

Cleaning and dressing are performed in a plant, recently constructed, north of the river. This plant is of steel frame construction, with a galvanized corrugated steel roof, and open on all four sides. The wire-rope tramway discharges into a receiving bin, from which a belt conveyor extends to a mill storage bin of 200 tons' capacity. The barite is fed to two Woodburry jigs, which remove most of the quartz and rock.

Heavy mineral is discharges into a bucket elevator and raised to a second bin, from which is fed to an 8 ft. x 36 in. Hardinge mill, operated in closed circuit with a drag classifier. The overflow `is pumped to a nest of four cone classifiers, the underflow returning to the Hardinge mill and thew overflow passing over a screen, to remove chips; and thence to a Dorr thickener. A Dorrco pump removes the thickened pulp and discharges into a mixing tank and thence to a splash box beneath a film drier. A revolving splasher throws the pulp against the drum of the drier, 5ft. in diameter and 14 ft. long, as it slowly revolves. The drum, of welded construction with trunnion inlet and outlet, is heated by live steam supplied by an oil fires boiler, 150 hp., Scotch marine type. A wooden hood and stack remove the vapor. About 9 gal. of fuel is required to dry one ton of barite. The pulp, which adheres to the drum as a thin film, is rapidly dried as the drum revolves. Scrapers remove the deposit of fine dry barite and carry it by screw conveyors and elevator to the Rotex screens above the finished bin into which the product is received. From the bin the barite is discharged by a revolving rake to the center discharge, and delivered by screw conveyors and elevators to four sacking machines, designed at the plant. A small diameter screw conveyor feeds the material to the funnel about which the sack is attached. The sack is supported on a scale. When the weight of barite within the sack reaches 100 lb., the feed screw is automatically stopped. The final product, 99.95 per cent through 325 mesh, contains about 94 percent barite. It is used principally for oil-well work, as described in Engineering and Mining Journal of March 8, p. 224. An interesting feature in the cleaning practice is the floating of quartz in the ball-mill discharge. By reducing the proportion of water, a thick and heavy pulp is maintained in the grinding mill. This is of sufficient density to float quartz, which is removed by a short revolving trommel at the discharge end of the mill. The pulp passes the screen, and the quartz particles are discharged from the open end of the trommel. An equal v olume of water and barite gives a mixture with a specific gravity about equal to that of quartz. By reducing the amount of water, a mixture of a specific gravity close to three can be obtained. It thus becomes feasible to float the quartz in the ball mill pulp.

The plant is electrically operated, receiving its power from hydro-electric transmission lines. Its capacity is 8 tons per hour. Total horsepower used is 400. At present, operated on a single shift basis, it is producing about 75 tons per day. E. H. Murchison is superintendent in charge.