The greatest period of mining activity in the Angels Camp area occurred in the early 1930s, after the Aetna Placer Mine was acquired by the Calaveras Central Gold Mining Company, Ltd., of San Francisco. The company acquired the mining rights to 837 acres, including the Victor, McElroy, Peirano/Aetna, and Reiner mines, the E.W. Johnson Ranch, the Slab Ranch, and other mines of the Calmo Mining & Milling Company (Julihn & Horton 1938:42). Officers of the company included Harry Sears, president; Desmond Sears, secretary, and C. P. Chamberlain, treasurer. W. H. Warwick was mine superintendent. Part of the property was acquired from the Victor Land and Mineral Co. about 1926, and the remainder from other holders in 1933 (Bradley 1936:329). At this time Warwick was residing in a two-story frame house, with a basement, located between the Aetna and Calaveras Central shafts (Castle 1987).

When visited by the State Mineralogist in 1936, the mine was described as being located along 3 ½ miles of the ancient auriferous Central Hill Channel, separated by stringers of Calaveras slate bedrock, with numerous quartz stringers which were planned to be developed at some future time. The mine was developed by a 350-foot three-compartment vertical shaft located midway between the various channels. Approximately 150,000 gallons of water per 24 hours were pumped out of the mine per 24 hours by a Sterling turbine pump, driven by a 30-h.p. motor (Bradley 1936:330).

At that time, the property had been opened up about 1,600 feet upstream with recent operations approximately 2,000 feet from the working shaft downstream. The Peirano (Aetna) shaft, 240-feet deep, was located about 800 feet southeast of the working shaft and used for ventilation and as an emergency exit. Mucking machines and a shovel underground loaded the gravels into 2-ton cars which were hauled to the surface by battery locomotives. The gravel and waste were hoisted in skips to a surface ore bin, with waste stacked by a 200-foot conveyor belt. Above ground, the gravels went to a 21- by- 5-foot trommel for washing and screening, while the undersize gravel was washed through a 24-inch sluice with a concentrating device and over 24 feet of Hungarian riffles. This material was dewatered and conveyed to a Leahy vibrating screen, then passed down to a concentrator. The slime discharge from the concentrator was hoisted by a bucket elevator and conveyed to a tailing dump. Production varied from 75 to 200 tons daily. Other equipment on site included a double-drum electric hoist, two Sullivan single compound compressors, sawmills, blacksmith and machine shops, large change rooms, first aid building, office and other structures. Fifty-five men were employed working three shifts per day (Bradley 1936:331).

According to the Mineral Industries Survey of the United States, Bulletin 413, published in 1938, the Calaveras Central was by then the largest drift mine in California. Its management had pioneered the application of more effective engineering methods to produce large tonnage at low cost (Julihn & Horton 1938:42).

When taken over by the Calaveras Central, the property had three shafts: the three-compartment 350-foot Reiner shaft, the 240-foot Aetna shaft, and the 200-foot McElroy shaft. The Reiner was reconditioned to become the main Calaveras Central, the Aetna was re-timbered to become the exit shaft, and the McElroy was planned to be re-timbered to rework that area. The room-and-pillar method of mining was used (Julihn & Horton 1938:46-48).

During the early 1930s, over 30,000 feet of workings opened more than 4,000 feet of channel, a new steel 100-foot headframe was constructed to replace the older 65-foot one, new storage bins were built, and new magnetic vibrating feeders, washing plant, and trommels installed. Development work continued intermittently until 1942 (Clark and Lydon 1962:86). Harry Sears was mine superintendent during this phase of operation. Several articles in the local newspaper recounted the installation of machinery, modernization of the mine, and big strikes during the first year of operation (Harris 1931).

According to Guy Castle, who worked in the mine from 1931-1933, three shifts of nine or ten men each were working around the clock in the drifts and the mill. The rock was run through a trommel where the large material was screened out and dumped in large piles. The material which went through the 5/8-inch screen was then run through a 200-foot long sluice box. The amount of gold recovered each day was equivalent to three-fourths of a gold pan.

Castle noted that water for the milling operation was obtained from the mine, which produced 360 gallons per minute, although in earlier years a ditch was used which brought water from Lane Reservoir, just north of the mine, and the ditch which was still operating in the 1920s. This was part of the Utica Ditch system, which took over the earlier Union Water Company’s facilities, and the reservoir was named for the Utica mine superintendent, Charles Lane (Castle 1987).

During this period of operation, the Calaveras Central was described as a “model mine, continuing to make improvements, keeping production costs below $2.00 per ton, and demonstrating the utility of modern mass-mining techniques in drift gravel operations” (Limbaugh and Fuller 2004:278). The mine, along with all others in Angels Camp and Altaville, was shut down during World War II by Executive Order L208.

In 1947 rehabilitation work again began on the Calaveras Central properties, and by 1950, a new 600-tons-per-day mill, new surface equipment, and a 110-foot steel headframe were installed. The headframe was designed and built by local mining engineer Bernard Monteverde, assisted by Clarence Hale and Dick Bassley (Castle 1987; Schmauder 1987). Some of the old workings were reopened and the main shafts re-timbered (Clarky and Lydon 1962:86). Guy Castle recalled that little work was done on the property during this period and that it only operated for about three years, with Clarence Hale as the superintendent.

In December of 1960, the mine property was purchased by neighboring rancher Romie Rolleri for $21,000 at a tax sale. In December of 1961, Harry Sears attempted to save the property, but was unable to come up with the money for back taxes (Calaveras Enterprise December 9, 1960). When purchased by the Rolleri family, all the blacksmith tools were still to be found in the blacksmith shop, the men having walked away and left the one of the most productive Calaveras mines to history (Limbaugh and Fuller 2004:308).

Another attempt to reopen the mine was made by Michael Miller in 1979. Miller was operating the adjoining Amazon Star and Altaville Mining Company property to the north, but after some preliminary work in dewatering the Calaveras Central, work was halted. Most of the equipment was removed from the mine, and only the headframe, hoist house, a portion of the mill house, and some concreter footings remain on the site.