LuxRender Materials Metal
From LuxRender Wiki
The Metal material uses measured data to render a variety of realistic metals. This material does not accept custom colors or paramters. The shiny metal material should be used instead of you want dyed metals or need something you do not have an NK file for.
There are 4 built in presets you can select from: gold, copper, aluminum, and amorphous carbon. There is also an option to load measured data from an NK file in the Sopra or Luxpop format in order to use other metals.
This determines how shiny the material is by varying the roughness of microfacets. If your exporter uses the exponent to control roughness, higher values are shinier, with 0 being matte. If your exporter uses the direct roughness control, lower values are shinier, with 0 being a perfect reflector and .80 being matte. Values between .80 and 1 are an unrealistic "super-matte" and should be avoided.