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Ironsand, also known as iron-sand or iron sand, is a type of sand with heavy concentrations of iron. It is typically dark grey or blackish in color.
It is composed mainly of magnetite, Fe3O4, and also contains small amounts of titanium, Silicon dioxide, manganese, calcium and vanadium.
Ironsand has a tendency to heat up in direct sunlight, causing high enough to cause minor burns. As such it forms a hazard in New Zealand at popular west-coast surf beaches such as Piha.
The ironsand is mixed with the other sands as small grains of black or dark-blue magnetite. Sand used for mining typically had anywhere from 19% magnetite to as low as 2%. The ironsand typically had to be separated from the sand mixture. Because the magnetite is usually heavier than quartz, feldspar, or other minerals, separation was usually done by washing it in (a method similar to gold panning but on a larger scale). Sluice separation typically yielded concentrations of magnetite ranging from 30 to 50%, depending on the type of sand and the method used. In the early 20th century a process of magnetic separation was developed that could produce concentrations as high as 70%. Dabieshan: Traditional Chinese Iron-production Techniques Practised in Southern Henan in the Twentieth Century by Donald B Wagner – Curzon Press 1985 Page 31–32 Once concentrated, the magnetite grains could then be Smelting into various forms of iron. However, the loose, granular nature of the ore was difficult to keep contained in common bloomeries or blast furnaces, having a tendency toward granular flow (mimicking a liquid at larger scales) and was easily blown away by the bellow blasts, so was impossible to process using common methods of iron or steel production. Thus, innovative methods of smelting the ore were developed. The magnetite grains, however, often contain other metal impurities, such as chromium, arsenic, or titanium. Graphics and Text in the Production of Technical Knowledge in China by Francesca Bray, Vera Dorofeeva-Lichtmann, Georges Métailié – Koninklijke Brill Nv 2007 Page 616 Due to the nature of the sand, the mining operations were rarely stationary, but frequently moved from place to place.
Donald B Wagner, an expert in ancient Chinese metallurgy, notes that attempts to trace the history of ironsand in China end with inconclusive results. One source may indicate its use as early as the Tang Dynasty (~700-900 CE) while others seem to contradict this interpretation. Due to wars, invasions, famines, distrust of the government, overpopulation, a rising opium epidemic, and clashes between various tongs of miners, very little information exists about the industry between the 11th century and the 19th century, when a European miner named Felix Tegengren arrived to find the Chinese industry in shambles. Tegengren notes that ironsand was sluice mined in Henan and Fujian by local farmers and smelted over charcoal fires to make tools, but it involved a lot of work, which made it very expensive. It was only smelted where there was enough wood for the fires and cheaper steel was not readily available. Therefore, the material was considered to be economically unimportant in China. The Chinese in America: A History from Gold Mountain to the New Millennium by Susie Lan Cassel – Altamira Press 2002 Page 43–46 However, because the mining was safe, outdoor work, it was practiced by local farmers to supplement their income wherever it was available; in the 19th century of sluiced sand typically sold for the equivalent of 50 to 60 US dollars (by 2016 exchange rates ~ 900–1000 dollars or 700–800 euros).
However, in the modern age ironsand is Placer mining along China's southeast coast and used for smelting steel. The typical composition of this ironsand is 48.88% metallic iron, 25.84% silica, 0.232% phosphorus, and 0.052% sulfur.
The ironsand in Japan comes in two forms. Masa ironsand is found mixed with quartz sand that washes down from granite mountains. The magnetite in the sand contains few impurities or other metal oxides. Masa ironsand was used for manufacturing wrought iron and steel, used in everything from tools to cookware. Ironsand was used extensively in Japan for iron production, especially for traditional Japanese swords. Akome ironsand is found mixed with sand made from an igneous rock called diorite. The magnetite in the sand contains often greater than 5% titanium dioxide, which lowers the smelting temperature. The akome ironsand is used in the tatara to make pig iron, which is then used to make items out of cast iron ( nabegane). In the manufacture of steel, the akome was added to the tatara during the initial stage of smelting, acting as a binder and catalyst for steel production, upon which the masa ironsand was poured during further stages. When smelted for pig iron, or 120 kanme) typically yielded about of pig iron, of steel, and of slag. When smelted for steel, of sand yielded about of steel, of slag, and of pig iron. Slag and pig iron that were not suitable for use were then melted together to form wrought iron, of which mixed produced about of iron. The Mining Industry of Japan During the Last Twenty Five Years, 1867-1892 by Tsunashirō Wada – Director of Mining Bureau, Department of Agriculture and Commerce Japan 1893 Page 235
New Zealand had limited deposits of iron ore, but the deposits of ironsand were massive. It had been used by some early settlers to manufacture steel and pig iron, but the material could not be smelted in common bloomeries or blast furnaces. The New Zealand mining handbook by New Zealand. Mines Dept, P. Galvin – John Mackay 1906 Page 494–495 A few smelting companies formed in the late 19th and early 20th centuries, but were unable to process the ore with any economic success due to the sandy nature and high titanium content, which tended to form hard, brittle carbides in the steel. In 1939, a commission was formed to study the properties of the ore and devise a way of smelting it on an industrial scale. The commission determined that, by sintering the sand into bigger chunks or pellets, the problems of smelting the sand in a blast furnace could be eliminated. DSIR: Making Science Work for New Zealand : Themes from the History of the Department of Scientific and Industrial Research, 1926–1992 by Ross Galbreath – Victoria University Press 1998 Page 182 However, at that time World War II began, and thus further development was suspended and did not resume until the late 1960s, producing the first output of steel in 1969. DSIR: Making Science Work for New Zealand : Themes from the History of the Department of Scientific and Industrial Research, 1926–1992 by Ross Galbreath – Victoria University Press 1998 Page 170–200
Ironsand is placer mined from Waikato North Head. 1.2 million tonnes is used by New Zealand Steel to create steel, in a unique manufacturing process. Mining at Taharoa produces up to 4 million tonnes for export. A previous mine existed at Waipipi in South Taranaki. A proposal by Iron Ore NZ Ltd. for further ironsand mining off the coast of Taranaki Region faced resistance from some Māori and others in 2005 in the wake of the New Zealand foreshore and seabed controversy. A large quantity of it is shipped to China and Japan, but by 2011 New Zealand's sole manufacturing plant was producing 650,000 metric tons of steel and iron per year. New Zealand is the only country to use ironsand for industrial smelting. The typical composition of the magnetite is 82% iron oxide, 8% titanium dioxide and 8% silica; 0.015% sulfur, and 0.015% phosphorus. In 100% concentrations of magnetite this had a maximum potential to yield ~ 58% metallic iron, although the titanium is unrecoverable by modern techniques. The New Zealand mining handbook by New Zealand. Mines Dept, P. Galvin – John Mackay 1906 Page 486–487
However, Japanese craftsmen have been using sand-iron in sword-making for at least 1200 years. The crafting of sand-iron in "tatara" smelters, made of brick and clay, is still practiced by Japanese craftsmen today.
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