By Roger W. Burdette, special to CoinWeek …..
Every place that produces or proclaims a special product has its own “biggest,” “best,” or other claim to something superlative. In the prime of gold-mining times, states and mining territories competed for such superlatives. “Biggest gold strike,” “deepest mine,” and other claims were common for their promotional value in enticing investors and the fleeting opportunity to generate local pride. One of these that got newspaper attention was the title “largest gold bar in the world.”
A lot of gold is needed to make a large gold bar, normally much more than a mining operation produced in a single clean-out of their sluice boxes and leaching ponds. This meant it took weeks or months to accumulate enough gold to make a sizable bar. It also required furnaces large enough to melt the gold and cast it into a single mass. Plus, once a big bar was cast, what good was it? Gold was money and time was money, so every mine owner wanted to get their precious metal to market so they would have money to pay the bills and build luxurious residences to show how “smart” they were.
American gold miners appear to have made only two exceptionally large gold bars during the 19th century. First came a bar weighing 6,127.78 troy ounces produced by the North Bloomfield Hydraulic Mining Company in Nevada County, California in October 1882. The second was cast from the output of three Montana mines and weighed 6,995 troy ounces. We’ll explore these bars in more detail, but first, let’s look at how the gold in these bars was acquired.
The Bloomfield Bar
North Bloomfield operated a hydraulic mine. This is a type of surface mining that resembles placer mining using a sluice box (or trough) but on a much larger scale. As with an individually operated placer mine, gravel, clay, dirt, gold grains, and rocks are put at the upper end of a sluice and washed with water. The resulting mud flows down the trough and out the lower end. Along the way, heavy gold is trapped in irregularities (called “riffles”) while lighter material is washed out at the end and discarded (called “tailings”). This will all be familiar to anyone who has viewed popular television shows about Alaskan and Yukon mining.[1]
In hydraulic mining, gold is separated from gravel, sand, and clay along entire hillsides or cliffs sprayed with high-pressure water to dislodge material. This mudflow is directed toward large sluices where, as with our small example, gold settles into riffles in the sluice.
Figure 1. Hydraulic mining using high pressure water cannons at the Malakoff Diggings, 1877. These water streams were very powerful—they could throw 185,000 cubic feet of water in an hour with a velocity of 150 feet per second. The environmental destruction they could do was also powerful. (Photo by Carleton E. Watkins. University of California, U.S. Geological Survey.)
Hydraulic mining presents fewer risks and more certainties at a lower cost than any other form of mining.[2] The hardest work was done by Chinese immigrants who dug water channels leading to sluices and built wooden frames. Sluices were much less efficient than those shown in modern TV programs, and it’s worth taking a few moments to describe their construction. A typical wooden sluice was an open-top trough about 11×11 inches. Planks making up the bottom and other joints were fitted tightly together so that no water (or gold) could slip through. “The sluice should be lined on each side with two 11-inch by 13-inch planks, nailed to the sluice, to protect it; and the lower edge of this lining should be 1-inch above the bottom of the sluice. This enables the ‘riffle strips,’ which separate the blocks forming the false bottom, to be laid in and taken out easily.”[3]
Figure 2. Long wooden sluice showing position of riffle blocks. The base of the closest row shows the 1-inch spacer that produces a gap where gold collects. (Photo by W. S. Welton from Thomas S. G. Kirkpatrick Hydraulic Gold Miner’s Manual, London. 1890. 2a.)
Riffles were made “from wood blocks 10-½ inches square and eight inches deep, placed on the bottom of the sluice. They were separated by strips of wood 11×1-inch laid across the bottom of the sluice. These were held in place by small wedges and could be easily removed without damaging the sluice.”[4] The muddy water had to move over the riffle blocks fast enough not only to keep light material in suspension but also allow gold to sink between the wood blocks. A commonly accepted grade was a three-foot fall for every 100 feet of length (three percent).[5] This is sufficiently rapid to allow the gravel to travel down the sluice, get thoroughly washed and disintegrated, and set free the tiny particles of gold mechanically mixed with it.[6] A sluice for hydraulic mining might be 1,000 feet long, so clean-out was a major event.
Figure 3. Cross section of a typical 19th century sluice showing position of blocks and lining. Rows of blocks were separated by one-inch wide spacers which created a gap where gold collected. (Thomas S. G. Kirkpatrick Hydraulic Gold Miner’s Manual, London. 1890. 7a.)
When the mine boss felt that the riffles were filled, he ordered a cleanup. This involved removing the riffle blocks, cleaning them in a water tank, shoveling out all the accumulated concentrated gold pay dirt (called “concentrate”), and rinsing the sluice clean. The concentrate was taken to a guarded building where workers removed iron particles with magnets and further processed material to remove dirt. The result was native gold and silver that was later melted with the addition of borax or other fluxes to remove the remaining slag.
The 6,127.78-troy-ounce bar from North Bloomfield was the result of a single cleanup after 20 days of continuous running.[7] This bar contained 0.897 fine native gold, and 0.093 fine native silver[8] for a total value of $114,280.72 broken down as:[9]
The gold was poured at the Nevada City foundry using an iron mold produced at Clipper Gap, California. Dimensions of the gold bar were 15 inches long, six inches wide, and seven inches deep for a volume of 630 cubic inches.[10] Previously, large bars valued at $35,000, $41,000, and $40,000 from hydraulic mines in Butte County, California had been reported. These were followed by bars worth $71,273 and later $90,000.[11] In November 1882, the Bloomfield bar was sent to the Bank of California in San Francisco and broken up for refining and coinage.[12]
In December, Henry C. Perkins[13] donated a plaster model of the bar to the California State Mining Bureau Museum.[14]
The Broadwater Bar
Our second contender for the largest gold bar came from Montana and was more a publicity stunt than a legitimate example of mine production. We’ll call this the “Broadwater” bar. It was cast at the insistence of Charles Arthur Broadwater, President of the Montana National Bank, the largest such institution in the Territory.[15]
The Broadwater bar was cast at the Helena Assay Office on September 3, 1889, by combining three smaller bars. One bar from the Spotted Horse Mine was of high-quality native gold and worth more than $58,000 (over half the total). Two other bars containing greater proportions of silver came from Drumlummon and Jay Gould mines. In shape, the Broadwater bar was a truncated pyramid, the base being 18×7½-inches, the height 7½-inches and the top surface 17×6 inches. Its weight was 6,995 ounces[16] and its value was $101,355.50.[17] The bar assayed at approximately 0.689 fine gold and 0.311 fine silver, making the gold worth $99,604 and silver $1,751.50. This unusually low proportion of gold made the bar what the United States Mint called “silvery gold.” One newspaper commented, “In appearance it is not as handsome as the Spotted Horse bar (which was the true golden yellow), the silver it contains destroying the color. But it is a good sight nevertheless.”[18]
Figure 4. Small veins of gold scattered through a matrix of quartz and other minerals. This is the most common mineral form of hard rock gold mining (courtesy Reeds Prospecting, Western Australia).
In addition to being a composite of several smaller bars, the Broadwater example was mined in a costlier and much more dangerous process. All three contributing mines were hard rock operations. In this type of mining, tunnels are dug into the earth in places suspected of having veins of valuable minerals–gold, silver, copper, coal, or anything else of commercial value. Gold was often associated with the mineral quartz and scattered throughout the matrix, not in convenient flakes and nuggets as in placer mining.
Figure 5. Copper Queen mine, Cochise County, Arizona, in 1883 with extensive timbering to support the ceiling (courtesy Western Mining History).
Mines varied from simple dead-end tunnels to vast arrays of connected passages created when miners followed natural gold-rich veins. Occasionally, unusual circumstances led to the creation of odd-looking support structures or steeply angled tunnels.
Figure 6. Miners in Butte, Montana lighting fuses of the explosive-packed holes of a rock face (courtesy Western Mining History).
Once ore was pulled from a mine, separating valuable metal from the waste rock was not always easy. While gold, silver, and copper are sometimes found in their elemental state and not associated with other metals, that is infrequent except for placer gold. Milling was used to separate the waste. This was usually a two-step process: crushing the ore into fine particles and treating the crushed ore to separate the valuable mineral content from the waste rock.[19]
Stamping
Stamp mills (or occasionally “crushing mills”) operated by running rough ore under a bank (or “battery”) of iron hammers that broke the ore into smaller particles. By using several batteries in sequence, rocks could be reduced to sand-size grains or even powder.
Figure 7. A small stamp mill with five hammers at an abandoned Nevada mine. Excentric gears make the hammers rise and fall (Photo by Tami, “Nevada Ghost Towns & Beyond.” )
Following stamping, the ore could be treated in several ways to separate gold from the common rock dust. We’ll briefly mention these to help readers understand the basic process.
Roasting
This was a pre-separation process intended to improve gold recovery from associated minerals, especially sulfides like iron sulfide (FeS2), often called iron pyrite or “fool’s gold”. Heating the crushed ore to a high temperature oxidizes the sulfur and expels it into the surrounding air (this works best when the ore is finely crushed). Ordinary rock salt was often added to improve the oxidation of sulfides.
Once roasting was complete, the extraction of gold or silver from the ore by chemical treatment was faster and more efficient than without roasting.[20]
Amalgamation
The element mercury is liquid at room temperature and forms a solid alloy with gold and silver called an “amalgam”. This process was accomplished in many ways, all of which involved mixing finely crushed and roasted ore with mercury. The amalgam was then heated to vaporize the mercury, most of which was recovered by a copper distillation hood.
In large processing mills, long plates of mercury-coated copper were placed directly under the discharge of the stamp mills. The finely crushed ore was mixed with water and slowly distributed over the plates. The resulting amalgam was scraped off the plates and pressed into cakes to recover as much mercury as possible. The remaining gold was filled with cavities and called “sponge gold”. This sponge was melted, mixed with various fluxes to separate the remaining dross, and cast into bars.
Cyanidation
While there are many different processes to remove gold from its encapsulating ore, cyanide leaching (cyanidation) is perhaps the most common and well-known. A cyanide solution (NaCN or KCN) was elevated to a high pH level (>10.5pH) so that free cyanide (CN-) dissolves the gold in the ore. It had been long known that gold is soluble in a potassium cyanide solution, but it was not until the late 1880s that an organized, patented process of using cyanide to dissolve gold spread quickly throughout the western mills.
A cyanide solution was sprayed onto large vats or outdoor “heaps” (as in piles) of finely crushed ore to be dissolved. The leach solution was collected in a tank, and other chemicals were used to precipitate gold or silver.[21] In the United States, thiosulfates have supplanted cyanides for this purpose.
Casting
Regardless of the extraction means, gold had to be melted and poured into iron molds to form bars. This allowed the mixing and assay of multiple small deposits at the assay office and greatly simplified handling and security. Each bar was stamped with its purity and weight and often a control number that referenced the original deposit and owner of the gold.
Figure 8. Pouring molten metal into a mold. In this instance the crucible (or melting pot) likely held 1,000 T oz. or less of gold or silver. (Deadwood Assay Office photo, Library of Congress.)
There are no known photos of casting the Bloomfield and Broadwater bars, but the 1913 photo above shows the basic process. The primary difference between 1882, 1889, and 1913 is that the size of the crucible and hoist machine was larger.
Casting the Broadwater bar was no small task. At noon on September 3, Spruille Braden, Assayer-in-Charge of the Helena Assay Office, handed out the necessary gold. This was placed in a No. 100 crucible – the largest size made. This crucible was first placed on an intensely hot fire, which was made hotter still by a bellows. The crucible was barely large enough to hold the gold. It required a long time to melt the precious metal, particularly because the original bars had not been cut down to a smaller, more easily melted size. After about eight hours of work, in which six men were engaged, the crucible was attached to iron tackle and hoisted from the fire. An iron mold, made especially for this bar, was at the ready. The workmen, with their heads wrapped in damp cloths to protect them from the intense heat, tipped the crucible to an incline and the silvery-yellow metal poured slowly into the heated mold.[22] The mold was moved to a vault for cooling, and even by 10 the next morning it remained warm to the touch.[23]
On September 9, a stag dinner was given to the assay office men by Mr. Broadwater and Mr. Phelps[24] in recognition of their work in melting, calculating, and finishing the great $100,000 gold bar to be exhibited by the Montana Bank at the Fourth Annual Minneapolis Industrial Exposition of 1889. Messrs. Braden, Myendorff, Kelly, Walker, Gillespie, Bradshaw, Hill, Denbow, and Metten participated in the festivities, and, after washing away the cares of office in the Hotel Broadwater swimming pool, they enjoyed as good a dinner as the hotel was capable of providing.[25]
A day after casting, the Broadwater bar was sent to the Expo and displayed beginning September 6.[26] The bar was the topping piece of a “mineral mountain” of Montana products. The base consisted of four large bars of lead, four bars of copper on top of that, four bars of silver for the third layer, and on top of the whole was the Broadwater gold bar. The monument was surrounded by specimens of quartz, gold nuggets, and mineral samples from all parts of the Territory.[27] After two weeks in Minneapolis, the entire exhibit was shipped to New York where it was displayed in the outer office (“lobby”) of the Chase National Bank.[28] One Montana newspaper writer predicted, “It is safe to say that such a magnificent exhibit will create a furor in the East and will advertise Montana as no other exhibition has yet done.”[29]
The Montana Record-Herald newspaper chortled that:
The pilgrimage of bankers and railroad presidents caused a steady stream of visitors to the Chase National Bank today, where is on exhibition something which made many mouths water. The big brick of gold, the biggest ever run into shape from any assay office, was sent by the Montana National Bank at Helena, Montana, in which city it had been turned out by the United States Assay Office.[30]
A policeman with a big nightstick and two heavy revolvers was on guard day and night.[31]
After the display closed in mid-October, the Broadwater bar and other gold and silver items were sent to the New York Assay Office for refining and casting into normal bars ready for coinage at the Philadelphia Mint.
The biggest gold bar in the world, containing 6,127.78 T oz of fine gold, was the 1882 output of a single clean-out in one mine, made by the North Bloomfield Hydraulic Mining Company. Broadwater’s Montana National Bank bar, containing 4,819.56 T oz of fine gold was a poor second, its weight being distorted by nearly one-third of silver.
But what of today? Is there a “Largest Gold Bar in the World” in the 21st century? Turns out, there is.
Figure 9. World’s largest gold bar weighing 8,038 troy ounces and worth about $17,638,600 (courtesy Mitsubishi Materials Corp and Toi Gold Museum).
The hefty paperweight shown above is 250 kg (8,038 T oz) of 0.9999 gold. The world’s largest gold bar measures at base 455 mm × 225 mm (17.9 in × 8.9 in) and 170 mm (6.7 in) high with a five-degree draft angle. Its volume is 15,730 cm3 or 960 cubic inches. It was manufactured by the Mitsubishi Materials Corporation, a subsidiary of Mitsubishi. It went on display at the Toi Gold Museum in Izu, Shizuoka, Japan, on July 11, 2005. Its gold content was valued in May 2024 at about $17,683,600.[32]
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Notes
[1] North Bloomfield and other hydraulic mines were deeply involved in litigation (Woodruff v. North Bloomfield Gravel Mining Company) concerning pollution and damage to the Yuba River and the town of Marysville downstream from the mines. The large gold bar appeared at the end of October 1882 during active court arguments. It is possible the bar was made to impress politicians and Judge Lorenzo Sawyer with the economic loss that might result if hydraulic mining were prohibited. In 1884, the Court ruled in favor of Woodruff. Later, bucket dredging of the Yuba River tailings produced several million dollars in additional gold.
[2] Theodore F. Van Wagenen. Manual of Hydraulic Mining, Fourth Edition. New York. 1913. 7.
[3] Thomas S. G. Kirkpatrick. Hydraulic Gold Miner’s Manual. London. 1890. 7.
[4] Ibid.
[5] Modern usage is a somewhat steeper five-percent grade.
[6] Kirkpatrick. Op.cit. 3.
[7] “Nevada County Items”, The San Francisco Examiner. October 29, 1882. 8.
[8] “Collections Made by the State Mining Bureau”, Catalogue of the State Museum of California, Vol, 2. Sacramento. 1884. 130.
[9] At approximate current market prices at the time of writing of $2,200 per ounce for gold and $29 per ounce for silver, the bar would be worth about $12,092,608 in gold and $19,816 in silver for a total of $12,112,424.
[10] “Big Gold Bars”, Free Press. Redding, California. September 21, 1889. 7.
[11] Ibid.
[12] “The Business World”, The San Francisco Examiner. September 8, 1889. 16.
[13] “Collections Made by the State Mining Bureau”, Catalogue of the State Museum of California, Vol, 2. Sacramento, 1884. 130.
[14] “Mining Museum”, San Francisco Examiner. December 29, 1882. 4.
[15] Montana became a state on November 8, 1889. The capital city was and is Helena. There was a United States Assay Office located in the city.
[16] “A $100,000 Bar”, The Montana Record-Herald. September 4, 1889. 8.
[17] “Montana’s Achievement”, The Independent-Record. Helena, Montana. September 4, 1889. 4. Some newspapers state the weight as 6,954, which this author believes to be a misprint.
[18] “A $100,000 Bar”, Op. cit. This was similar to the alloy electrum, often seen in ancient gold coins.
[19] Carter, Gary. “Winning the Metal: Ore Mills of the West”. Accessed May 23, 2024.
[20] Ralph, Chris. “Smelting and Roasting Gold and Silver Ores”, Nevada Outback Gems.
[21] Carte. Op. cit.
[22] “Montana’s Achievement”, The Independent-Record. Helena, Montana. September 4, 1889. 4. Minor editing for accuracy.
[23] “A $100,000 Bar”. Op cit.
[24] Louis G. Phelps, VP and Acting Cashier of Montana National Bank in 1889. In 1903, he bought the Pitchfork Ranch in Wyoming and eventually expanded the property to 250,000 acres. In December 2023, a 96,000-acre remnant was offered for sale for $67 million.
[25] “Past and Prospective”, The Independent-Record. September 8, 1889. 6. Edited. The day’s work, fuel, and other expenses are not mentioned in the Helena Assay Office’s financial reports, nor is the bar mentioned in any other United States Mint documents. Payroll records for the first week of September 1889 have not been located. Thus, the Assay Office work was either off the books or quietly reimbursed by the Montana National Bank.
[26] “Exposition Notes”, The Saint Paul Globe. September 7, 1889. 6.
[27] “It Beats the World”, The San Francisco Examiner. September 5, 1889. 2.
[28] “The Largest of all Ingots”, Pittsburgh Dispatch. September 25, 1889. 4.
[29] “A $100,000 Bar”. Op. cit.
[30] “That Big Bar”, The Montana Record-Herald. September 24, 1889. 8.
[31] “The Largest of all Ingots”. Op. cit.
[32] “Mitsubishi makes record-size gold bar”, Japan Times. June 17, 2005. Updated value.
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