Tungsten

Tungsten cannot be found as a native metal. Its main ores are feberite, hubernite, scheelite, and wolframite. Feberite, hubernite and wolframite are very closely related chemically and they are usually placed together in a group known as either tungstates or wolframates. They have very small differences, which are that feberite has iron and tungsten and huebnerite has tungsten and manganese, and wolframite has tungsten, iron and manganese. Feberite has a black color to it, huebnerite is sort of a reddish brown, and wolframite is either dark brown to nearly black. There are a number of minerals that that resemble these tungsten ores and they need to be assayed in order to be identified. They have a metallic luster, a hardness of 4.5 to 5 and a specific gravity of 7.1 to 7.5. Scheelite is quite simple to prospect with a fluorescent light given that it turns blue or yellowish in short-wave ultraviolet rays. In its natural form it looks like quartz and a lot of scheelite deposits have been found by simply using a fluorescent light on quartz surfaces that have been examined before. In its natural form its color is white however it has been found in brown and green crystals as well. It has an adamantine luster, a hardness of 4.5 to 5 and a specific gravity of 5.9 to 6.1.