This lovely semi precious gemstone cabochon material is known as Rainbow Pyrite or Iridescent Pyrite.
It comes from Ulianovsk, Russia. It is collected on the banks of the Volga River only during the summer months when the riverbanks are less muddy.
This material is considered a type of Druse. Druse, (also sometimes spelled drusy or druzy), refers to a fine layer of miniature crystals coating a matrix rock.
Rainbow Pyrite has a metallic look, with a shimmering rainbow of colors: including shades of gold, green, pink and blue. The matrix is silicified mud concretions. When the mud dried and cracked the pyrite formed in the cracks.
Pyrite is the classic "Fool's Gold". There are other shiny brassy yellow minerals, but pyrite is by far the most common and the most often mistaken for gold. It is so common in the earth's crust that it is found in almost every possible environment, hence it has a vast number of forms and varieties.
Metaphysical properties of Rainbow Pyrite: Rainbow Pyrite is an excellent shield from negative energy. It symbolizes warmth, love and friendship.