The J. A. Mendes mine was a 48.68 acre placer mine one and one-half miles south of cool and west of Highway 49.
The Jacob C. Baughman mine was a 27.85 acre placer claim one mile south of Omo Ranch. It was part of a large group of similar claims in one area.
The James S. Kennedy mine was a 40 acre placer claim three and one-half miles northeast of Placerville.
The James Skinner, Jr. and Alex D. Skinner mine was a 160 acre placer claim two and one half miles west of Rescue, just to the north of Green Valley Road. The James Skinner, Jr. mine was a 140 acre adjacent placer claim. The Skinner winery was located at the intersection of Green Valley Road and Cameron Park Drive. Parts of it remain.
The Jap mine was a 20.34 acre lode gold mine on the west branch of the Mother Lode one-half mile south of Greenwood.
The Jay E. Russell mine was a 67.70 acre placer claim two miles east of Volcanoville.
The Jennings mine was a lode gold mine on 17.23 acres, two miles southeast of Kelsey between Rock Creek Rd. and the South Fork of the American River, just west of Rock Creek.
The Jerome and Guiseppi Tunzi mine was a 40 acre placer claim on Ringgold Creek, two miles east of Diamond Springs.
One and one-quarter miles east of Placerville was a placer gold mine called the Jerusalem mine. It was not much more than a gravel deposit prospected by hydraulicking in 1894.
The Jinkerson and Arditto mine was a drift, placer gold mine at Indian Diggings. Active in 1913-17 and in 1926, it was developed by and adit several hundred feet along an ancient river channel.
The Joerger mine was a chromite mine eight miles west of Shingle Springs. This mine was first worked during World War I, but most of the ore was removed in 1942. The exact tonnage of the removed ore is not known because it was combined with the output of other mines. Estimated ore reserves are 10,000 to 15,000 tons of 5 percent to 8 percent chromite in alternating rich and lean layers. In 1942 an open pit 150 feet long, 15 to 40 feet wide and 25 feet deep, produced ore averaging 8 percent chromite.
The John and James Blair mine was a 160 acre placer claim three miles east of Placerville just west of Chunk Creek. The John Blair mine was a placer claim adjacent to the south boundary of the City of Placerville as it existed in 1938. There was another James Blair claim of 160 acres on the north fork of Weber Creek, one and one-half miles south of Camino.
The John A. Holden mine was a 35 acre placer claim one and one-half miles east of Latrobe.
The John C. Andreason mine was a 160 acre placer claim one mile south of Indian Diggings.
The John C. Berry mines were a series of placer claims consisting of 160 acres all in the vicinity of Garden Valley.
The John H. Ferretta mine was a 60 acre placer claim one-half mile west of Newtown.
The John S. McClellan mine was a 160 acre placer claim on Camp Creek, two and one-half miles east of Pleasant Valley.
The John Steely mine was a placer claim on 80 acres adjacent to the Mother Lode, one-half mile north of Placerville.
The John W. Rupley mine was a 40 acre placer claim one mile east of Smith Flat.
The Johnson mine was a placer mine two miles northwest of Lotus near the South Fork of the American River.
The Jones (Good Luck) mine was a lode gold mine two miles south of Diamond Springs. it was active in 1915 and during 1922-23 when several thousand dollars of gold was produced. The deposit was developed by a shaft with levels at 75, 165 and 225 feet and several drifts.
Five miles northwest of Georgetown, at Jones Hill, was the Jones Hill placer mine. A gravel channel eight feet thick and 200 feet wide, over slate bedrock, was hydraulicked around 1892 and again in 1907.
The Joseph Immer mine was a 30 acre placer mine two miles northwest of Lotus and north of Highway 49.
The Joseph Skinner (Fisk, Porphyry) mine was a seam gold mine on the Mother Lode, one mile north of Placerville. It was active 1896-98, 1901-03 and around 1932, with a total output of nearly $100,000. Consisting of thin quartz seams and small quartz bunches it was originally worked by hydraulicking and later by a crosscut 90 feet deep at the face, running west 232 feet, with drifts. Most of the gold was specimen gold, taken from pockets and kept intact, although small lots were milled.
The Joseph Snow and Co. mine was a placer mine consisting of 160 acres on the North Fork of Weber Creek, one mile south of Camino. This should not be confused with the nearby Snow Consolidated placer mine that is still in operation as rock quarry.
The Josephine mine was located at the town of Volcanoville. It was a six-foot vein of lode gold in slate and serpentine developed by five drift adits, actively mined in 1889-90, 1896, 1920, and 1934-35. The ore was treated in a 20-stamp mill.
There was also a Josephine placer mine on 43.54 acres of land near Volcanoville.
The Josh Billings mine was a lode gold mine on 20.43 acres of the west branch of the Mother Lode one and one-half miles northwest of Garden Valley.
The Juckes placer mine was located on 40 acres, two and one-half miles south of Latrobe on the Cosumnes River.
The Julia Beard mine was a lode gold mine on the Mother Lode two and one-half miles south of the town of El Dorado.
The Kates (Norris) mine was a placer gold mine located one and one-half miles east of Volcanoville. It was active prior to 1894 and again in 1896, when it was prospected by the Two Channel Mining Company, a company involved in a number of placer gold mines. This ancient river gravel deposit was originally hydraulicked and later developed by a 250-foot bedrock adit and several drifts. The cemented gravel was treated in a stamp mill.
The Katherine mine was a lode gold claim on the Mother Lode, two miles south of Diamond Springs.
The Keegan mine was a lode gold mine on the Mother Lode in the City of Placerville.
The Kelly mine was a chromite mine active around 1918. It was located just east of Rattlesnake Bridge and, during World War I, 25 tons of ore was produced, containing 28 percent chromite. Like many other early mines in the area, it is now under Folsom Lake.
Another Kelly mine was an early lode gold mine, located on the Mother Lode just east of the town of Kelsey. It was later renamed the Dalmatia. Numerous quartz seams and a quartz vein were found in a zone that varied in width from 20 to 50-feet, which were worked in the 1880’s, 1890-94 and again around 1935. A two-foot vein assayed at $16 per ton, a single pocket yielded $14,000 and the seams yielded around $2 to $3 per ton. The mine was originally worked in an open cut some 500 feet long and later was developed by a 200-foot inclined shaft and a 1200-foot adit. The ore was treated on site in a 10-stamp mill.
A third Kelly mine was a lode gold mine located on the Mother Lode one-half mile north of Kelsey. On the Kelly Ranch and owned by Miss Margaret Kelley, the deposit consisted of a six-foot wide vein of gold bearing quartz in Mariposa slate. It was active around 1902 and 1932 and developed by two 50-foot shafts, 150 feet apart.
The Kelsey Gold and Silver (Lady) mine was a lode gold mine on 41.67 acres of the Mother Lode about one mile south of Kelsey. Originally worked prior to 1915, it was reopened in 1926 and a mill erected that year when the Kelsey Mining Company was formed. The Kelsey Mining Company operated it until 1931, when it again closed. In 1934 the mine was reopened and operated until 1941. The ore, which was found in narrow bands of quartz, contained free gold, pyrite and some galena (lead ore). During the years 1928-1931 15,000 tons of ore was crushed that yielded from $1.80 to $6.40 per ton. It was developed by a main 1700-foot north drift adit and a 700-foot north drift adit about 300 feet above the main adit. These two adits were connected by a raise and there were several crosscuts. There was also a 42-foot shaft near the main adit portal (opening). Originally the ore was treated in a ten-stamp mill, which was later replaced by a Telsmith gyratory crusher and an Aurora jaw crusher. About 40 tons of ore per day were processed at the mine.
The Kenna mine was a placer gold mine one mile northeast of Kentucky Flat, several miles east of Georgetown and about two miles east of Volcanoville. It was active up until 1896 when it was operated by the Two Channel Mining Company. Some additional work was done as late as 1922. The two gold bearing gravel channels were worked by different means, the Main or White channel was hydraulicked and the Blue channel developed by a 1500-foot adit. The coarse gold was held in well cemented gravel that was treated in a 10-stamp mill.
The Kennebec Bar mine was a placer mine on the Middle Fork of the American River about two miles northeast of the town of Cool.
The Kentucky Flat mine was located at Kentucky Flat, about two miles southeast of Volcanoville. It was later known as the Kentucky Flat Consolidated placer mine and consisted of 674.30 acres on two different ancient riverbed channels. The mine was active in 1894-1902 and again in 1933. It was another mine operated by the aptly named Two Channel Mining Company. As with the Kenna Mine, the Main or White channel was hydraulicked – this time in a pit with a 25-foot bank – and the Blue channel developed by a 625-foot adit and an 80-foot shaft.
The Keystone mine was a lode gold mine on 8.63 acres of the Mother Lode about one-half mine northwest of Placerville.
Near Georgetown, during the years 1947 and 1948, the Knight Placer Mining Company operated a dragline dredge to remove placer gold from various gravel deposits.
Three miles northeast to Georgetown on Little Bald Mountain was a chromite mine known as the Knoff (Austin) mine. The mine was active twice: in 1918 when 400 tons of ore were mined and again in 1942-44 when 79 tons were mined. The deposit consisted of pods and lenses of chromite in sheared serpentine that was developed by open cuts and shallow shafts.
The Kumfa or Kum Fa mine was a placer gold drift mine at Smith Flat. It was Active from 1911-13 and also in 1928 and 1936. The ancient river gravel deposit was developed by a 631-foot inclined shaft. It was worked in conjunction with the nearby Carpender mine.