Although not as well known as the more common metals like iron and copper, tungsten (chemical symbol W) is a metal of many outstanding properties.
Some of these are that it has:
- The highest melting point of all elements except carbon (3422°C). A temperature of about 5,700°C is needed to bring tungsten to boil - which corresponds approximately to the temperature of the sun's surface
- Excellent high temperature mechanical properties and the lowest expansion coefficient of all metals.
- A density of 19.25 g/cm3, making tungsten among the heaviest metals. Its electrical conductivity at 0°C is about 28% of that of silver which itself has the highest conductivity of all metals.
These and other properties allow tungsten to fulfil many specialised tasks both in the industrial world and around the home. Many of these uses are discussed on the Primary Uses page of this website.
Tungsten at King Island is found in the form of scheelite, which has the chemical composition of CaWO4. Scheelite has the unusual property that it fluoresces under ultra violet light, making it easy to spot in the host rock.1
Although more than 30 tungsten-bearing minerals are known, only two of them are important for extraction: wolframite (Fe,MnWO4) and scheelite (CaWO4). The concentration of these minerals in workable ores is usually 0.3-1%W03.1
World tungsten resources have been estimated at 7MtW, including deposits that have so far not been proven to be economically workable. It is suggested that 30% of these resources are wolframite and 70% are scheelite ores. The former mineral contains 76.5% WO3, while the latter contains 80.5% WO3. There are major deposits of these minerals in China (with about 57% of the world total), Russia, Austria and Portugal.1
1 Mining Journal Special Publication - Tungsten June 2008