“They say you can see the whole universe in opals, that’s how old they are,” says Howard Ratner as he gazes upon a raw ... stone). Red is one of the rarest shades found in a black opal.

iridescent blue colours. The opal weighs 443.56 carats, or around 90 grams. It was listed as the world's largest black opal - considered the rarest form of the gemstone - in the 1990 Guinness Book ...