Nuummite is usually black in colour and opaque. It consists of two amphiboles, gedrite and anthophyllite, which form exsolution lamellae that give the rock its typical iridescence. Other common minerals in the rock are pyrite, pyrrhotite and chalcopyrite, which form shimmering yellow bands in polished specimens.
In Greenland the rock was formed by two consecutive metamorphic overprints of an originally igneous rock.The intrusion took place in the Archean around 2800 million years ago and the metamorphic overprint was dated at 2700 and 2500 million years ago.The formula is (Mg2)(Mg5)Si8O22(OH)2
and hardness 5.5-6.
Greenland is the only location in the world where this material is found.
Size: 8x8x5.7 mm.