This shader is very similar to marble shader in that it also mixes two colors using noise() and turbulence(). The difference is in how the mixing is done. The two colors are mixed without treating them separately in any way.
ambient is a value between 0.0 and 1.0 which determines how much of the base color of a surface that is visible when it is not illuminated by any light source.
specular is a value between 0.0 and 1.0 which is the fraction of color specularly reflected.
c3 is the shininess of the surface where 0.0 is the most dull and 1.0 is the most shiny.
scale describes how much the texture coordinates should be scaled before applying the granite texture. The larger the scaling, the smaller the area of the granite texture associated with a given area of the surface. A large number results in a very fine pattern, a small number yields a coarse pattern.
color1 and color2 is a list containing the red, green and blue values for the base material. Each being a number between 0.0 and 1.0.
opacity describes the opacity of a surface. 0.0 means totally transparent, 1.0 means totally opaque. May be a list of red, green and blue opacity values or a single value to be used for all color channels. Optional, default is 1.0.