Conrad mine
Conrad mine was a silver and base metals mine at the locality of Howell, on the western slopes of the Northern Tablelands, within the New England region of New South Wales, Australia. The mineral deposit that was exploited by the Conrad mine was a complex ore body, containing silver, lead, zinc, tin, arsenic, and copper ores, with some gold as well. From 1906, the Conrad mine's operations also included the workings of the adjacent King Conrad mine. The ore body, primarily, was worked for its silver content, but other metals and minerals were also produced. The mine was operated, between 1898 and 1913, with two interruptions, and from 1953 to 1957. It produced over 3,500,000 ounces of silver. The mine was well known as a source of rare mineral specimens.
History of operations
Discovery and early mining
The presence of silver in the area had first been noticed in 1888. Small scale mining took place, but expectations of a silver boom were dashed when it was found that much of the complex ores could not be smelted, even after being taken at great expense to the smelter at Newcastle. Initially, miners extracted only the purest ores from shallow workings. The deposits in the area near Bora Creek were described in Government Geologist Edward Pittman's 1901 work, The ''Mineral Resources of New South Wales.'' The deposit consisted of a rich but complex lode, with quartz gangue, intruding into surrounding granite rock. The edges of the lode carried areas of rich silver-lead ore, and mineralisation was also dispersed throughout the quartz. Pittman noted that the Cockle Creek smelter did not accept ores from Bora Creek for smelting due to the presence of stannite.Early operations (1897—1899)
The first deposit that would be exploited commercially at scale was found in 1890. In 1897, the mining lease was bought by John Howell, and it become the Conrad mine. It is probable that the Conrad mine was named after one of Howell's grandsons, Conrad George Howell Blakemore, born in 1897.Howell was intrigued by the problem of processing the valuable but complex ores. An unusual feature of the deposit was that it contained almost entirely sulphide ores, with almost no oxide ores. Government Geologist, Edward F. Pittman, wrote regarding the deposit that, "probably no similar combination of valuable metals on a large scale has ever been worked before". When Howell had a 100 foot deep shaft sunk, in 1898, the feasibility of mining the ore body was proven. Early reports of the new mine stated that the lode was four feet six inches wide and that a ton of the ore contained 170 ounces of silver, as well as its lead content. However, it would take, until 1912, to completely solve the problem of recovering an optimal amount of the valuable content of the complex ore.
By mid-1899, there were two large mines operating in the area. The first was Howell's mine, which had become known as the Conrad mine, and the other was Alwell's claim, which became the King Conrad mine. By August 1899, there was a third mine, the Bora Creek Extended, later to be known as the 'South Blocks', 'Conrad South Blocks' or 'Conrad South' mine. The mines were all on the same line of lode and each become owned by a separate listed company.
The opening of the mines lead to the formation of a mining village, named Howell, after John Howell. The main street of Howell was Conrad Street, and it continued from the village to site of the Conrad mine.
Conrad Silver Lead Mining Company (No Liability) (1898—1903)
A company, Conrad Silver Lead Mining Company, was formed in August 1898. The authorized capital of the company was £25,000 in £1 shares, paid to 10%. Subscribers were John Howell, his wife 'Lizzie' Howell, Howell's daughter, Maude Blakemore, son-in-law George Blakemore, and three others; Mary P. Adams, H. Edwin Moore, and Richard Festus O'Rourke, who was nominated as manager of the venture. From January 1899, O'Rourke was Vice-Consul of the United States of America in Sydney and he was also secretary of Howell Consolidated Gold Mines, another venture associated with Howell. The new company seems to have acquired the mine, from John Howell, at a value of £6,000.At the time that the company was floated, Howell had not long resigned as general manager of the Smelting Company of Australia, the company that owned and operated the Dapto Smelting Works.
Howell's approach to processing the complex ore of the Conrad mine was to separate the component minerals, by gravity separation, into fractions that could be successfully smelted, and subsequently further refined. In 1901, the concentrator plant was reported to produce one ton of concentrates and slimes from every three to four tons of run-of-mine ore. The capacity of the mill was reported to be around 280 tons of ore per week.
The mined ore was first thrown onto a 'grizzly'. Coarser material was hand picked and the richer lumps processed by a Blake rock crusher. After crushing that ore, together with all the ore that passed through the 'grizzly', was crushed in a set of Cornish rolls, and then passed to a trommel. Coarse material from the trommel was recycled through the Cornish rolls and trommel. The fines of ore that passed through the trommel were treated in May jigs fitted in four compartments; No. 1 compartment produced galena concentrate; No. 2 produced mispickel and lead concentrates; No. 3 produces copper and mispickel concentrates; No. 4 produces copper concentrate. The concentrates from No.3 compartment were recycled through the jigs, to further separate the mispickel and copper concentrates. The tailings from the jigs were treated in Wilfley vanners, while the slimes pass from the jigs to settling tanks, with the overflow from settling tanks collected in the dam.
King Conrad mine (1899—1904)
A mining lease adjacent to the Conrad mine's lease, was taken up by a local prospector, Peter Alwell, and became the King Conrad mine. Alwell and his partners sold the King Conrad to a Melbourne syndicate, for £60,000, in April 1900.By December 1900, there was a well-equipped mine and concentrator under construction. The first meeting of new company held in June 1901 was optimistic about the future of the mine.
The mine started its mill in February 1902. By that time, the mine was down to 400 feet. The King Conrad used a similar approach to that used by the Conrad mine, separating the minerals by gravity separation.
By July 1902, the King Conrad company had run out of capital, and the mine was idle. A petition was made to wind up King Conrad Silver and Lead Mining Company in August 1902, and the company went into liquidation, in September 1902. There was an unsuccessful auction of its leases and assets, in January 1903; the company owed £12,000 to Union Bank of Sydney, as mortgagee.
By late 1902, it was apparent that the King Conrad mine would not survive alone, and rumours circulated that its mining operations would be combined with those of the adjacent Conrad mine. However, that combination would not to happen, until 1906, although the moves to do so were underway by 1904. In August 1903, there was talk of work in the King Conrad mine resuming under a new company. In November 1903, it was reported that six men were employed there making a drive toward the Conrad mine workings.
During late 1904, an English syndicate began working the King Conrad mine. H. Edwin Moore took over management of the mine, during the 12 month option. He also managed the adjacent properties of Consolidated Conrad Silver Mines. In August 1905, the syndicate extended their option to purchase the mine. The same syndicate also held an option to purchase over the properties of Consolidated Conrad Silver Mines.
The problem of stannite (1900—1903)
As mining progressed, more stannite was found, some in massive ore form, but also diffused through the other ores. That became a particular problem, as no smelter wanted stannite—a hitherto rarely found copper-tin-iron sulphide mineral, Cu2FeSnS4—and other metallic ore concentrates containing stannite were penalized by smelters, basically by not paying the mine for any of their valuable tin content. Stannite ore later caused the failure of another mine, the Tolwong Mine, on Shoalhaven River, near Bungonia.At first the stannite was stockpiled, while Howell worked on a solution for a method of recovering valuable tin metal from the stannite. Wilfley tables were added to the concentration process, and Howell experimented with smelting the stannite in a water jacket furnace, at the mine site. He achieved success in mid 1903.
Howell's method was to smelt the stannite-rich ore and thus separate it into two salable products; an argentiferous copper matte—containing over 60 per cent copper and 300 ounces of silver per ton—and a tin-lead metal alloy—55% tin and 45% lead—which was cast into tin-lead bullion. There was a market for such materials, which could be refined further. Smelting lead ore to metal is a reduction reaction, whereas production of copper matte involves an oxidisation of the sulphide ore. Howell stated that the lead-tin was recovered from the ore, as a first step, but a smelting process that involves both reduction and oxidizing reactions was a remarkable achievement.
Any gold in the ore—and there was a very small amount present—would also end up in the matte, with the copper and silver. A refinery would first convert the matte to impure metallic 'blister copper'. The next stage of refining would be to separate the copper from the gold-silver, by electrolytic refining, producing pure 'cathode copper'. The remnant sludge was than converted to dore bullion, an alloy of gold and silver, which could be refined further.
By 1903, John Howell was around 70 years old, and his mine manager son-in-law, George Blakemore, was fully occupied in far away Cobar. The Howell family were trying to dispose of their interests in the Conrad mine and management responsibility, and seeking new investors and management to take it over. With the problem of the stannite ore appearing to have been resolved, the mine seemed to have a bright future, albeit with more capital needed. However, in 1906, doubts would emerge about whether the problem of treating the complex ore had really been solved completely.