Other variations focus on specialisms within the profession; for example Blacksmith, from those who worked predominantly with iron, Whitesmith, from those who worked with tin (and the more obvious Tinsmith), Brownsmith and Redsmith, from those who worked with copper (Coppersmith and Greensmith; copper is green when oxidised), Silversmith and Goldsmith – and those based on the goods produced, such as Hammersmith, Bladesmith, Naismith (nail-smith), Arrowsmith which in turn was shortened to Arsmith, or Shoesmith (referring to horseshoes). Sixsmith is variant spelling of a sickle- or scythe-smith. Wildsmith in turn is a corruption of wheelsmith