Dutch Flat Mining District (Towle Mining District), Placer Co., California, USAi

Regional Level Types
Dutch Flat Mining District (Towle Mining District)	Mining District
Placer Co.	County
California	State
USA	Country

A former Au-Ag-Pt-Cu-Zn-Fe-Pb-In mining area located in secs. 2, 3 & 4, T15N, R10E and in secs. 26, 27, 33 to 36, T16N, R10E, MDM, about 10 miles NE of the town of Colfax, next to the Nevada County line. Discovered in 1849. The Dutch Flat District is primarily a placer gold district having produced from thick sections of exposed Eocene auriferous channel gravels. Only minor production was obtained from a few small lode mines. The district also includes a few rather insignificant asbestos and chromite mines.

Location: Dutch Flat is in north-central Placer County. This district includes the Alta and Towle areas. The district includes all gold-quartz lode and placer mines in the vicinity of the communities of Dutch Flat, Monte Vista, Alta, and Towle, and for the most part, north of the former Southern Pacific Railroad (currently Union Pacific) line. The Gold Run district lies just to the south, the You Bet district to the west, and the Lowell Hill district to the northeast.

The Dutch Flat District includes numerous small, individual mines distributed throughout an area encompassing approximately 8-10 square miles on the northwest flank of Moody Ridge (once known as Dutch Flat Ridge), north of the Union Pacific Railroad and Interstate 80 and south of the Bear River. Since the majority of workings were located around the community of Dutch Flat, the community itself was chosen to represent location of the district. The location latitude and longitude identify the USGS 3,144-foot elevation benchmark located near the center of the community on the USGS Dutch Flat 7.5-minute quadrangle (approximately center of Sec. 34, T15N, R10E, MDBM). Dutch Flat is reached by taking Interstate 80 east for approximately 25 miles past Auburn to the Dutch Flat exit. The town is one mile north of the exit, on Sacramento Street.

History: Placer mining began here in 1849. The settlement was established by some Germans or "Dutch" in 1851. Hydraulicking began in 1857 and, during the following few years, the hydraulic mines were highly productive. Operations continued until 1883, when the mines were shut down by anti-debris injunctions. Some work was done in the district again in the 1890's and early 1900's. Logan (1936) estimated the district to have a total output of $4.5 million to $5 million (period values), although it may be more. The old town of Dutch Flat is well-preserved and is now a popular tourist attraction.

Placer mining in the Dutch Flat District began with the discovery of modern placer deposits in the gravels of the Bear River in 1849. Dutch Flat was established in 1851 when two German brothers, Joseph and Charles Dornbach, made camp on the bluff overlooking the Bear River. Local miners originally called the camp "Dutch Charlie's Flat," but when the town was granted a post office in 1856 it was formally named Dutch Flat. Besides its prominence as a mining center, it became a stage and railroad station, making it one of the largest, and most important towns in the county from 1864 to 1866. In 1859, a possible rail route was proposed through Dutch Flat and across the Sierra. The railroads realized the value of the proposed route and the Central Pacific Railroad became a reality. The first shares in the venture were subscribed in Dutch Flat. In 1866, after the railroad had reached Cisco, 20 miles farther east, Dutch Flat lost much of its importance as a stage stop.

As the modern placers in the Bear River played out, attention turned to the Eocene gravels on the bluffs north of Dutch Flat as the miners migrated from the river canyon to these new grounds. By the late 1860's, the construction of the railroad had caused Dutch Flat's Chinatown to become one of the largest Chinese settlements outside of San Francisco (Logan, 1936).

While the Bear River placers paid well during the early years and limited drift mining of the Eocene blue lead gravels was proving productive as early as 1856, it was the introduction of hydraulic mining in 1857 that caused the town and district to flourish. Hydraulic mining commenced on small individual claims such as the Phoenix, American, Buckeye, Dutch Flat, and Queen City claims. While the claims were small, the yield was high. In October 1859, the Placer County Canal was completed to Dutch Flat providing sufficient water to implement large-scale hydraulic mining. Several individual claims were productive, but there are no detailed records for any of the early mines. However, the Badger Claim reportedly produced $192,000 (period values) in dividends in four years. During the following five years, the hydraulic mines were highly productive. At Dutch Flat's peak during the 1860's, approximately forty-five hydraulic claims were being worked within a 1.5-mile radius of town. A production of about $150/day was the average for a claim using 250 inches of water and employing 4-6 men (Logan, 1936).

By 1867, most of the easily washed upper gravels had been worked, and the first shaft was sunk to bedrock on the Buckeye claim to exploit the lower Eocene blue lead on bedrock. In 1867, the first milling of the hard gravel occurred on the Ohio claim. Subsequently, most blue lead gravels between Dutch Flat and the Central Pacific Railroad were worked by drifting (Logan, 1936). Almost no information is available about these early mines. Most were unpatented and in later years were relocated under other names.

During the 1870's, hydraulic mining operations reached their peak. In 1872, the Cedar Creek Company of London purchased and consolidated over 30 claims. They introduced large scale hydraulic mining and reportedly produced "millions."

Dutch Flat was one of the first mining camps where newly invented dynamite was extensively used in hydraulic mining to break up and collapse the gravel faces. The hydraulic mines in the area continued to produce fantastic amounts of gold well into the 1870's. A Chinese company reportedly found a $12,000 (period values) nugget in July of 1877. The gold at Dutch Flat assayed as high as .970 fine.

Activity essentially ceased in the district after the 1884 Sawyer Decision injunctions, which affected debris disposal. By as early as 1876, the Dutch Flat hydraulic mines had already deposited tailings 70 feet deep in the Bear River below. Plans to remedy this situation by driving a 3-mile tunnel under Moody Ridge and sending the debris to the North Fork of the American River were considered too expensive and thus abandoned (Logan, 1936).

By 1890, almost all of the mines were idle and the town was partially deserted and decaying. Since the deeper blue gravels were known to be rich, efforts were made to consolidate smaller claims on the channel and open the deeper channel for drifting.

In 1895, the Polar Star and Southern Cross Mines (Sec. 34, T16N, R10E) were operated by drifting, followed by renewed hydraulic mining of the coarse blue lead gravels. In 1900, the Polar Star was using 2,800 inches of water under 450-foot head with 8 and 9 inch nozzles. This was only enough water to permit work for 5 hours a day. A log debris dam was built in the Bear River and was used jointly by this mine and the Liberty Hill Mine in Nevada County to the north. Drift mines that were active about the same time were the Dutch Flat Blue Lead Mine, which worked a cemented bottom gravel that required crushing in a 10-stamp mill, the Alta Mine, and the Bartley Consolidated Mine, which was on the branch channel coming from Alta. The latter two mines produced low-grade gravel from a drift-mining standpoint.

After 1914, there was no hydraulic mining, and drift and quartz mining were drastically reduced county-wide. By 1916, the only gold mines reported to be "active" in the district were the Rawhide Quartz, Federal Drift, Dyer Drift, Dutch Flat Drift, Haub Drift, Indian Hill Drift, Moody Ridge Drift, and Stewart Drift. Of those, only the Dyer Drift and Stewart Drift were reportedly producing, the remainder undergoing only assessment work (Waring, 1917).

In 1933, the Enterprise Leasing Company obtained mining rights under a number of Dutch Flat town lots to prospect unworked gravels underlying the town itself. They erected a mill, and a 125-foot shaft was sunk to basement with considerable drifting. Only 100 ounces of gold were reportedly produced during 1934, and the project was abandoned. In August 1935, Lyman Gilmore and Associates filed a mining location in town on a portion of the gravels that had been excluded from the 1876 town-site grant. There is no record of any work being done on this location. As of 1936, no significant mining was being done in the district (Logan, 1936).

Geology: This district is located at the junction of several major channels of the Tertiary American River. One channel enters the area from the Lowell Hill district on the NW, another from Lost Camp and Shady Run on the E, and a third from the Gold Run district on the S. The main channel then continues W and NW through Little York, You Bet, Red Dog, and Hunt's Hill. It has been estimated that 90 to 105 million cubic yards have been washed here. The gravels have a maximum depth of 300 feet, the lower 150 consisting of coarse blue gravel. The bottom gravels are well-cemented. Bedrock consists of slate, gabbro, quartzite, and amphibolite.

Throughout most of the Dutch Flat District, only the basement rocks of the Calaveras Complex and the overlying Eocene auriferous gravels are present. While thick sections of Oligocene to Pliocene Valley Springs and Mehrten Formation rocks are present to the south in the districts of the Forest Hill Divide, and northwest in the Scott's Flat District, they have been largely lost to erosion in the Dutch Flat District. Limited outcroppings of the Valley Springs and Mehrten Formations are present on the east edge of the district near Alta and Towle and along Moody Ridge to the south.

The main body of basement rocks within the district consists of a belt of north-northwest trending steeply dipping, slate, argillite, amphibolite, phyllite, chert, and metavolcanic rocks of the Calaveras Complex. Gabbroic and serpentinite intrusions are common to the east. Immediately west of the district, the Foresthill Fault, a steep easterly dipping thrust fault, cuts the Calaveras Complex. To the east of the district, the Goodyears Creek Fault of the Melones Fault Zone (Clark, 1960) separates the Calaveras Complex from partially to completely serpentinized peridotite of the Feather River Peridotite Belt.

Basal Eocene Auriferous Gravels:

Due to localized erosion of the Valley Springs and Mehrten Formations, the Dutch Flat and neighboring districts were known for their immense bodies of exposed auriferous gravel. The total area of exposed gravels in the district approached 1-2 square miles. The district is located at the junction of three tributary channels of the Eocene Yuba River. The main tributary flowed northward from the adjacent Gold Run District before turning sharply southwest in the Dutch Flat area. From there, it crossed the present Bear River about a mile west of Dutch Flat, and then flowed 2-3 miles through the You Bet District where it was mined at the Christmas Hill and Little York Diggings. It then turned sharply north and flowed through the Red Dog and Hunt's Hill areas to its confluence with the Yuba River near North Columbia. A second channel flowed southwest from the Lowell Hill District and merged with the main tributary at Dutch Flat. A third, smaller channel entered the district from the Shady Run area to the east and also joined the main tributary at Dutch Flat

The Eocene gravels at Dutch Flat achieve a maximum thickness of 300 feet and can be divided into lithologically and texturally distinct units. The lower unit, or ?blue lead? of the early miners, averages 150 feet thick, rests directly on bedrock, and contains most of the gold. It is generally confined to the wide channel troughs on bedrock and buried under thick sections of upper gravel. The main tributary channel at Dutch Flat forms a distinct trough about 300 feet deep in which bedrock is in part polished and hummocky and in part soft and decomposed. Channel grade is as much as 10 feet in 100 feet. Based on an analysis of 26 samples collected throughout northern Sierra Nevada, the lower gravel unit averaged: cobbles and boulders, 13% (with boulders of up to several feet); pebbles, 56%; granules and sand, 28%; silt and clay, 3% (Yeend, 1974). Cobbles can average over 8 inches in diameter, and boulders may reach 8-10 feet in diameter. There is relatively little sand. The lower gravels are generally immature and composed of bluish-black slate and phyllite of the Calaveras Complex, weathered igneous rocks, and quartz. Chlorite, amphibole, and epidote mineral grains are also common components. Lower gravels are well-cemented, more suited to drift mining, and generally required crushing in stamp mills. While no specific information is available for Dutch Flat, the lower gravels were reported to have yielded as much as $9/cubic yard in the neighboring Gold Run District. Almost all of the blue lead gravels in the district have been drifted.

The upper gravels form the majority of the Eocene gravel deposits and, unlike the lower gravels, are well-exposed in cliffs and bluffs along the old river channels. Their thicknesses vary significantly within the district. These gravels are much finer, with clasts seldom larger than pebble size and characterized by an abundance of clay and silt beds. Large-scale cross-bedding and cut-and-fill features are common. Upper gravels are mature; quartz predominates, and the heavy-mineral content consists almost exclusively of zircon, ilmenite, and magnetite. Unlike the lower gravels, chlorite, amphibole, and epidote are absent. Gold values in the upper gravels are low, often no more than $0.02/cubic yard. However, between Dutch Flat and Indiana Hill to the south, the upper sands were reported to average $0.11/cubic yard (period values).

Lode Gold Deposits:

A few small lode gold prospects and mines were reported within the Calaveras Complex bedrock in the district. None were significant producers, however, and almost no information is available.

Structural Disturbance:

With the exception of the westward regional tilting of the Sierra Nevada, there is very little evidence of any significant post-Cretaceous structural disturbance in the vicinity of the Dutch Flat District.

Regional geologic structures include the Melones Fault Zone and the Gillis Hill Fault Zone. Local structures include the Melones Fault Zone.

Mineral occurrence models information: Model code: 119; USGS model code: 39a; BC deposit profile: C01. C02; Deposit model name: Placer Au-PGE. Mark3 model number: 54; Model code: 273; USGS model code: 36a; Deposit model name: Low-sulfide Au-quartz vein; Mark3 model number: 27. Ore bodies are generally irregular, tabular, lenticular. Controls for ore emplacement included mechanical accumulation on irregular natural bedrock riffles and within river and stream-channel lag gravels, bars, and point bar deposits. Deposits are often enriched downstream of eroded gold-quartz veins in the bedrock channels. Ore shoots within mesothermal gold-bearing quartz veins. Host and associated rocks include Tertiary unconsolidated sand and gravel and Permian-Triassic slate and argillite of the Calaveras Complex. Local alteration is negligible to non-existent (none described). Local rocks include undivided pre-Cenozoic metavolcanic rocks, unit 2 (undivided).

Commodity Information: Placer deposits: Placer gold dust to large nuggets. The placer gold was approximatly .970 fine. Lode deposits: Free-milling, gold-bearing quartz veins. Ore materials: Native gold; Gangue materials: quartz and metamorphic gravels.

Mining Methods:

Hydraulic mining:

Hydraulic mining methods were first applied at Dutch Flat in 1857. Hydraulic mining allowed the bulk processing of large volumes of low-yield Upper Eocene gravels that would otherwise be unprofitable by other methods of mining. Hydraulic mining involved directing a powerful stream of high-pressure water through large nozzles called monitors, or "giants," at the base of a gravel bank, undercutting it and allowing it to collapse. Large gravel banks several hundred feet high were mined in this manner, but larger banks were often hydraulicked in two or more benches. In some cases, adits were driven into the exposed face and loaded with explosives to help break down the exposure. The resulting slurry of clay, sand, gravel, and gold was washed through sluice boxes to trap the gold. The sluice boxes were generally four feet wide and deep and often over a thousand feet long and lined with riffles or other devices to mechanically trap the gold. Mercury was added to amalgamate the finer gold. The remaining debris was indiscriminately dumped in the nearest available stream or river.

One of hydraulic mining's highest costs was in the ditches, flumes, and reservoirs needed to supply sufficient volumes of water at high pressure. A mine usually needed its own system of ditches and flumes to deliver water from distant and higher reservoirs or rivers. A mine might have 10-20 or more miles of ditches as well as dams and reservoirs, flumes, and tunnels. Several major ditches brought water to the hydraulic mines at Dutch Flat from the Bear, North Fork of the American, and Yuba rivers. At the mine site, the water passed through large iron pipes into the monitors. Hydraulic mining flourished for about 30 years until the mid-1880s when the Sawyer Decision curtailed debris disposal.

Another expensive undertaking was often finding an outlet for the debris. As the gravels were washed lower and lower in the ancient channel beds, it was often necessary to drive a tunnel through the bedrock channel rim to drain the workings into a nearby canyon.

The primary hydraulic mining operations in the Dutch Flat District were on the gravel exposures to the north and west of the town of Dutch Flat on the bluffs above the Bear River. Most hydraulic mining was focused on the poorly consolidated upper gravel unit of the Eocene gravels. In most cases, the hydraulic mining was preceded or followed by drift mining of the harder cemented lower blue lead gravels. Most of the hydraulic mining activity at Dutch Flat occurred as small individual operations on individual claims of only a few tens of acres. Two of the larger and more famous mines, the Polar Star and Southern Cross mines (Sec. 34,T16N, R10E) comprised 140 acres and were intermittently mined by hydraulic and drift methods. Along with several other smaller operations, these mines worked the gravels all the way to bedrock and are responsible for the large hydraulic workings immediately northwest of Dutch Flat. These workings, which comprise over a half-square mile, are known as the "Nichols Diggings.? Several other operations are responsible for the considerable bedrock exposures in the Blue Devil Diggings just west of town.

Drift mining:

Drift mining of the lower blue lead gravels at Dutch Flat commenced in 1856 and was followed in 1857 and later years by extensive hydraulic mining. Drift mining at Dutch Flat was far less extensive than in the more famous drift mining districts of the nearby Forest Hill Divide.
Drift mining involved driving adits and tunnels along or close to the lowest point in the bedrock trough of an ancient channel and following it up or down stream along the channel thalweg. While some deeply buried channels were originally accessed through vertical shafts, drainage problems and the expense of hoisting limited the use of shafts, which led to most drift mines being accessed through tramway and drain tunnels driven into bedrock below the channels.

Channels were usually located by gravel exposures on hillsides and terraces. Exposures of upstream and downstream gravels were called ?inlets? and ?outlets,? respectively. Where a ravine or canyon cut into, but not through an old channel, the exposure was called a ?breakout.?

The preferred method of developing an inlet was to tunnel through bedrock under the channel at such a depth and angle as to break through into the bed of the channel providing natural drainage. The overlying gravels could then be accessed directly through the tunnel or by periodic raises and drifts. Development of an outlet involved following the bedrock channel directly into the hillside, the incline of the bedrock providing natural drainage. Prospecting and developing a breakout was more difficult, since the exposed gravel could be in the basal channel or hundreds of feet up on the edge of the channel, making it impossible to locate a prospect tunnel with any certainty. The surest method of prospecting was to run an incline on the pitch of the bedrock. Another method was to sink a vertical shaft on the presumed channel axis. The former method proved superior since it involved less subjectivity and often uncovered paying bench gravels on edges of the old stream. Once the bed of the channel was located, it was prospected by drifts and cross-cuts to ascertain width, direction, grade, and the location, extent, and quality of pay. The tunnel entrances were generally in or near a ravine or gulch for easy waste- rock disposal.

Prospecting also included projecting the grade and direction of existing channel segments for distances up to several miles. Thus having determined a potential location, a prospect adit or shaft was driven to evaluate it. This was a common method of finding old channels where there were no surface exposures.

Access tunnels were driven in bedrock to minimize timbering and ensure a stable roof, through which raises were driven to work the placer gravels. Tunnels were generally run under the lowest point of the bed of the channel in order to assure natural drainage and to make it possible to take auriferous gravels out of the mine without having to hoist it. Working upstream in a channel with a uniform grade, the main tunnel could be run on the surface of the bedrock.

The main drifts were kept as straight as possible and in the center or lowest depression of the channel. To prospect the width of the channel, crosscuts at right angles to the drift were driven on each side to the rims of the channels or the limit of the paying lead. These were timbered and lagged in soft gravels, but not to the extent of the main drift. In wide pay leads, gangways paralleled the main tunnel to help block out the ore in rectangular blocks. In looser intervolcanic gravels, timbering was required and the main difficulty was preventing caving until timbering was in place. The looser gravels were excavated with pick and shovel.
Working drifts in the gravel beds and pay leads themselves were larger than the bedrock tunnels and usually timbered due to their extended and long-term use. In wide gravel deposits, as a precaution against caving, gravel pillars from 20 - 40 feet wide were left on each side of the drift. When the main access tunnel was in bedrock following the line of the channel, pillars were not required, as the tunnel in the gravel was only for temporary use in mining the ground between its connections with the bedrock tunnel. Raises to access the gravel were made every 200 - 400 feet as necessary.

The breaking out of gravel (breasting) was done from the working faces of drifts. Usually, 1 to 2 feet of soft bedrock and 3 to 4 feet of gravel were mined out to advance the face. When the gravels were well-cemented, blasting was required. Otherwise the material could be removed with picks. Boulder-sized material was left underground, and only the gravels and fines were removed from the mine.

Some mines were plagued by bedrock swelling. Both tunnels on and within bedrock were sometimes affected by the upward swelling of the bedrock. In these cases, heavy timbering was required and the tunnel floor had to be periodically cut and lowered to keep the tunnel open.

Soft or fractured slates were the most favorable bedrock. The surface was usually creviced and weathered enough that gold could be found to a depth of one foot in the top of the bedrock. Where sufficiently weathered and soft, this upper bedrock layer could be easily removed. If the surface of the bedrock was too hard to be worked, it was cleaned thoroughly, and the crevices and surface were worked with special tools to remove every particle of gold, before the boulder waste was thrown back on it.

According to the hardness of the gravels, they were either washed through sluices or crushed in stamp mills. Most of the lower gravel in the Dutch Flat District was highly cemented and required milling in a stamp mill.

Ventilation of mines was accomplished by direct surface connection through the use of boreholes and the mine shafts and tunnels. It relied on natural drafts, drafts by fire, falling water, or blowers. Within the mines, arrangements of doors were often used to direct the flow of air through the tunnels, drifts, and breasts.

In most drift mines, ore was removed by ore cars of 1- to 2-ton capacity. Car capacity was largely determined by the available power and tunnel size. In smaller mines, small cars were often pushed by hand. In larger mines using horsepower or trains, larger two-ton cars could be brought out in trains of 5-10 cars.

Noteworthy Mines in the Dutch Flat District:

Very little specific information regarding the numerous individual mines in the Dutch Flat District is available. The following descriptions are thus necessarily brief and may be incomplete.

Southern Cross and Polar Star Mines (Sec. 34, T16N, R10E):

The Polar Star and Southern Cross mines consisted of 140 acres within the heart of the district immediately northwest of Dutch Flat. These adjacent mines were first hydraulically mined for the poorly consolidated upper unit of the Eocene gravels. After the initial hydraulic mining, a thick section of basal blue lead gravel remained. In the 1890s these remaining deposits were drift mined. As of 1896, drifting had been conducted at different points on the claims in a lower gravel bank 160 feet high. The main tunnel was 300 feet long, and the deep bedrock channel was 40 feet wide. The gravel carried 80% boulders, which were left underground. Breasts were 7 feet high and 40feet wide and timbered with post and cap (Crawford, 1896). In 1885, the Polar Star Mine was reported to have produced a single quartz boulder that yielded $5,780. In later years, hydraulic mining was applied to the remaining blue lead gravels in the Southern Cross and Polar Star mines. William Nichols conducted this deeper hydraulic mining, which exposed bedrock throughout the large area called Nichols Diggings, northwest of Dutch Flat. Where the deep gravels had previously been drifted, the yield was $0.25/cubic yard, and where not drifted the yield was $0.40/cubic yard.

Alta Drift Mine (Sec. 36, T16N, R10E):

As of 1896, the Alta Mine had a main working tunnel 2,900 feet long within the blue lead gravel of the smaller Eocene tributary entering the district from the east. A 180-foot water-blast ventilation shaft tapped the tunnel at 2,400 feet. Three crosscuts in gravel were developed: one driven northwest was 120 feet long, and one driven southeast was 216 feet long. A third had just been started. About 30 to 40 carloads of gravel were broken in breasting each day. The gravel contained about 60% boulders and cobbles, which were stored in the mine. A wash dump held 200 cars of 1-ton capacity. A 400-foot flume discharged into Canyon Creek and used about 90 miner?s inches of water for washing (Crawford, 1896).

Mines: Southern Cross, Polar Star, Alta, Nichols Diggings, Blue Devil Diggings, Nary Red, Banner, Bear River Hill, Queen City, Cedar Creek, Dutch Flat Drift, Indian Hill Drift, Consolidated Junction, Comet, Canyon, Dyer Drift, Federal Drift, Flying Fish, Golden Shaft, Gould Group, Hoose, Haub Drift, Stewart Drift, Moody Ridge Drift, Garden Claim, North Fork, Bear River, Bear River Tunnel, Little Bear, Big Blue Quartz, North Star Quartz, and the Morgan Asbestos Mine.

Production Data: Although no exact figures are available, it has been estimated that 105,000,000 cubic yards of gravel have been washed at Dutch Flat. Jarmin (1927), in his report to the State Hydraulic Mining Commission, estimated that about 17,000,000 to 34,000,000 cubic yards of gravel remain unworked at Dutch Flat.

The total production of the Dutch Flat mines can only be guessed. The district was one of the leading hydraulic producers in the county and contained many small mines, some of which were later consolidated. The figure of $3,000,000 (period values) in gold production has been credited to the district by 1867. Logan (1936) estimated total district production at between $4.5 - $5.0 million (period values).

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