Peruvian blue opal is relatively rare and is only found in the Andes mountains near San Patricio, Peru. It is a very translucent stone with color similar to the Caribbean Sea. Depending on how the stone is cut it can be clear, scenic (showing varying degrees of color) or dendritic which has black fern like inclusions.This is the national stone of Peru and, unfortunately, in recent years dyed stones have been mass marketed by unreputable dealers as Peruvian Blue Opal. If the blue color is uneven you are probably looking at a dyed stone. Dyed stones are quite common and sell very cheaply at gem shows and on internet auctions.