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, silica, manganese, calcium and vanadium. Ironsand has a tendency to heat up in direct sunlight, causing temperatures high enough to cause minor burns. As such it forms a hazard in New Zealand at popular west-coast surf beaches such as Piha.
Occurrence Ironsand is found worldwide. Although the iron mineral composition of the ironsand is mostly magnetite, the sand is usually mixed with other types of sand that wash downriver or ashore from mountainous or underwater deposits. The exact composition of the sand mixture may vary drastically even in the same geographic region. In some areas the sand may contain mostly quartz, while in others the sand may be made primarily from volcanic rock such as basalt, depending on the types of minerals along the water's path. The ironsand is typically picked up along the way from beds, veins, or inclusions of magnetite, which may originate a great distance from the sand deposits, and washed downstream or along the currents with the rest of the sand. Being heavier than the other sands, it is often deposited in areas where the water experiences a sudden change in direction or speed, such as the widening of a river or where the waves ebb and flow against the shoreline. 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 sluice boxes (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%. Once concentrated, the magnetite grains could then be smelted 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. Due to the nature of the sand, the mining operations were rarely stationary, but frequently moved from place to place.
Asia Historically, ironsand was predominantly used in East Asian cultures; most notably in China and Japan.
China Ironsand had moderate, localized uses in China during the late Industrial Revolution, but was a rather unimportant commodity throughout the long history of the Chinese iron-industry. Unlike the rest of Eurasia and Africa, there is very little archeological evidence to suggest that bloomery smelting was used in ancient China. The Chinese countryside was rich in deposits that contained both coal, a fuel that burns at a high temperature, and an iron ore containing a high content of phosphorus. Around 1200 BCE the Chinese developed a method of smelting the rocky ore into pig iron, which was then remelted and poured into molds (cast) to form cast iron. Although the metal was very brittle, this method was able to produce iron in much greater volumes than bloomery smelting, and with vastly higher yields of metal per ore. By the 1st century BCE the Chinese iron-industry was by far the largest and most advanced in the world. By the 1st century AD they had developed puddling for the production of mild steel, crucible steel for the manufacture of swords and other weapons, and a chemical process of rapidly decarburizing liquid pig-iron to make wrought iron, using the oxidation properties of saltpeter (called the Heaton process, it was independently discovered by John Heaton in the 1860s). China remained the world's largest producer of iron until the 11th century, manufacturing large quantities of relatively affordable steel and iron. 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. 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 1,000 lb (450 kg) 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 mined 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.
Indonesia In Indonesia, iron sand is prevalent on the south coast of Java island.
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