Nuummite is a very rare metamorphic rock of volcanic origin. It was formed about 3 billion years ago. It consists of the amphibolic minerals gedrite and anthophyllite. It is named after the Nuuk region of Greenland where it was found. Nuummite is usually black opaque in color with golden bands of pyrite, pyrrhotite and chalcopyrite. The sparkling play of colors is caused by its fibrous structure (alternating fibrous layers). Due to a change in angle of view or lighting, Nuummit creates a phenomenon called iridescence. Its only site is in Greenland. This rare mineral is very often sought after by collectors and gem dealers.