Period 6 element niobium, occurs in the minerals tantalite, columbite and coltan (a mix of columbite and tantalite). Tungsten, also known as wolfram, is a chemical element with the chemical symbol W and atomic number 74. The word "tungsten" comes from the Swedish language "tung sten" directly translatable to "heavy stone", though the name is "volfram" in Swedish to distinguish it from Scheelite, in Swedish alternatively named "tungsten". A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as a metal in
Filler metal point than the base metal, so that the joint may be made by bringing the whole assembly up to temperature without everything melting as one. Complex joints, typically for jewellery or live steam boilermaking may be made in stages, with filler metals of progressively lower melting points used in turn. Early joints are thus not destroyed by heating to the later temperatures. Welding processes work around the melting point of the base metal and require the base metal itself to begin melting. They usually require more precise distribution of heat from a small torch, as melting the entire workpiece is