*hiller*

n. [ G., play of colors. ] (Min.) The peculiar bronzelike luster observed in certain minerals, as hypersthene, schiller spar, etc. It is due to the presence of minute inclusions in parallel position, and is sometimes of secondary origin. [ 1913 Webster ]

Schiller spar (Min.), an altered variety of enstatite, exhibiting, in certain positions, a bronzelike luster. [ 1913 Webster ]

n. (Min.) The act or process of producing schiller in a mineral mass. [ 1913 Webster ]