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California

Kern County

Big Blue Mine (a.k.a. Big Blue Group) : (35.43.40N by 118.26.02W; USGS Lake Isabella North map) As of 1969 this mine has been consolidated with the Sumner Group, which includes the Lady Bell Group. (See the Cove Mining District.) (Gold, Silver, Copper, Lead)

Coordinates for the general ore body of this underground, past-producer are 35.43.34N by 118.26.25W.

County Report 1, California Division of Mines and Geology, 1962, p97 : The Big Blue Group includes the Beauregard, Big Blue, Blue Gouge, Bull Run, Content, Frank, Jeff Davis, Lady Belle, Nellie Dent, North Extension Sumner, Red Hill, Sumner, Urbana and other mines and claims. It (they) is (are) located in most of Section 28, NW ¼ of Section 33, and parts of the E ½ of Section 21, T. 25 S., R. 33 E., MDM in the Cove Mining District, 1 ½ miles southwest of new Kernville, on the northwest shore of Lake Isabella. As of 1955 most of the claims were patented and owned by the Kern Development Company, C.S. Long-President, Box 157, Hayward, CA, and leased to Kern Mines Company, Ronald Tognazzini-President, 260 California Street, San Francisco, CA,

Lode gold was discovered in the Cove District by Lovely Rogers; in 1860, in the area now occupied by the Jeff Davis, Lady Belle, Bull Run, Frank, Urbana and Beauregard claims. Rogers, Thomas J. Oders and Joseph Caldwell formed the Beauregard Mining Company and erected an eight-stamp mill with wooden stamps. Other discoveries of gold were made in the surrounding area, and by 1870 several mines were in operation. Most of these mines were consolidated in 1875; by Senator J.P. Jones, who established the Sumner Gold and Silver Mining Company. A 16-stamp mill was installed and later enlarged to 80 stamps as daily production from the mines was increased. The mine shut down in 1883 following destruction by fire of the surface buildings and near-surface timber in the upper workings of the mine. Attempts by lessees to restore the mine to productivity were unsuccessful. Kern Development Company, the present owner, acquired the property in 1907. From 1935 to 1943, Kern Mines Incorporated carried on extensive development and mining activities which resulted in the production of several hundred thousand tons of ore yielding an average of 0.11 ounce of gold, 0.10 ounce of silver, 6,500 pounds of copper and 69,000 pounds of lead. From 1934 through 1943 recovery of gold, silver, lead and copper was valued at over $1,200,000. The mine has been idle since 1943. No reliable production figures are known, but the production has been estimated to be several million dollars.

The Big Blue mine area is underlain by pre-Cretaceous rocks of the Kernville series, Mesozoic granodiorite, and later Mesozoic alaskite and aplite dikes. The Kernville series includes metasedimentary rocks preserved as roof pendants in the granodiorite, and in the mine area, is composed of a gray mica schist, dark gray to salty phyllite, light-yellowish thinly imbedded quartzite and white recrystallized limestone. Medium-grained grano-diorite crops out in most of the area to the west and to the east of the mineralized zone in metasedimentary rocks. The alaskite is a fine-grained foliated rock, which crops out in a dike that trends generally northeast parallel to the main or Big Blue-Sumner shear zone. It is aboyt 1,500 feet wide and is several thousand feet long, extending mostly along the east side of the shear zone. Aplite is intrusive into the alaskite in numerous 2-foot to 4-foot-wide branching, interconnecting dikes. The aplite was followed by intrusion of silexite, a very fine-grained, bluish colored siliceous rock.

The principal vein system, the Big Blue-Sumner shear zone, is a sheared and faulted zone, as much as 125 feet wide, that strikes N. 30 o E., and dips 70 o NW. This zone, also known as the Big Blue-Sumner lode, is tracable along the surface for more than 8,000 feet. Its southern half is along a contact between granodiorite and alaskite, and the northern half coincides with contacts between granodiorite, alaskite and metamorphic rocks. Innumerable subordinate faults, splits and sheared zones comprise the main shear zone. Post-ore faulting is evident in brecciated and displaced segments of the mineralized “blue” vein quartz. Ore bodies generally coincide with the quartz veins in the footwall, hanging wall and central positions of the shear zone. One of the largest ore bodies was elliptical in horizontal section, 500 feet long, with a maximum width of 60 feet near the center. Ore shoots are in opened joints in both the footwall and hanging wall country rocks adjacent to the main shear zone.

A second vein system lies west of the Big Blue-Sumner shear zone. It strikes N. 60 o E., dips 60 o -80 o SE. and terminates against the northern portion of the Big Blue-Sumner shear zone. This system of veins, which is designated the Lady Belle system, traverses alaskite and granodiorite. The belt containing these veins is about 700 feet wide perpin-dicular to the veins and 1,200 to 1,400 feet long. In general, the ore bodies in this system are shallower, shorter and richer than those of the Big Blue-Sumner shear zone. The average width of the ore bodies in the Lady Belle vein system is 2 to 4 feet, and the average grade for the ore was $12 to $20 per ton.

Ore bodies of both systems are composed principally of “blue” vein quartz containing very fine to coarse free gold ranging from 650 to 700 fine. At least 50% of the gold particles are associated with sulfides, especially arsenopyrite, pyrite, galena and sapalerite; less commonly gold is enclosed in these sulfides. Other metallic minerals present in the ore are marcasite-FeS 2 , pyrrhotite-FeS, scheelite-CaWO 4 , molybdenite-MoS 2 , stibnite-Sb 2 S 3 , bismuthite-Bi 2 S 3 , chalcopyrite-CuFeS 2 , and silver chlorides. The nonmetallic gangue minerals are calcite, sericite, chlorite, barite and albite. Wall rocks have been altered by sericitization, chloritization and albitization.

More than a dozen shafts have been sunk during different periods of development of the Big Blue Group. The most important of these are the Sumner or Engine shaft, the Cove, Pearson, Big Blue and Lady Belle shafts. The Sumner shaft, the first shaft sunk, is near the south end of the Lady Belle and Big Blue-Sumner vein systems. This shaft was sunk to a depth of 400 feet with levels at depths of 80, 160, 260 and 300 feet. This is the shaft that was destroyed by the fire in 1883. The Cove shaft, 350 feet northeast of the Sumner haft, was sunk to a depth of 240 feet and contained three levels. The Pearson shaft, in Big Blue Gulch 500 feet south of the Sumner shaft was 80 feet deep and connected with the original Sumner shaft workings. The Big Blue Shaft, the principal shaft, was 510 feet deep and was sunk 650 feet south of the Sumner shaft. Drifts were extended to the oldest workings of the Sumner shaft on the 80, 160 and 260-foot levels, and also on the 360 and 400-foot levels. The 360-foot level extends more than 1,000 feet north of the shaft and intersects four ore shoots, which range in width from 4 to 60 feet, and are 200 to 540 feet long. The 460-foot level contains over 1,000 feet of drifts and crosscuts, mostly north of the shaft. The Lady Belle shaft, the principal shaft of the Lady Belle system, is 438 feet deep and provided access to about 2,500 feet of drifts.

Four crosscut adits connect with the Big Blue-Sumner vein from the east. The North “tunnel”, 500 feet northeast of the Cove shaft, was driven a few hundred feet west from Sumner Gulch to the level 160 workings. The Pioneer “tunnel”, driven west to the vein near the Sumner shaft, served as a haulage level. The Big Blue “tunnel” was driven 2,000 feet west from a point near the Kern River to the Sumner shaft. This adit was originally driven to drain the 260-foot level. It is now part of the property acquired by the U.S. Corps of Engineers for the Lake Isabella flood control project, as is the mill site, and both are beneath the spillway level of the lake. The fourth adit, known as the Graveyard or South “tunnel”, is about 1,100 feet southeast of the Big Blue shaft. It was driven 500 feet west to the Big Blue-Sumner vein.

The total number of feet of horizontal workings in the Big Blue mine has not been determined, but earlier reports (1940) suggest the at least 30,000 feet of horizontal workings have been driven on the Big Blue-Sumner vein. The extent of the workings of the Lady Belle system are even less well known. They probably aggregate a minimum of 10,000 feet.