Black Opal Cabochon Cut Gemstone

About Opal  –

Opal is hydrated silica with no crystal structure, and precious opal flashes with shifting colours as you turn it. That 'play of colour' comes from tiny stacked spheres of silica bending light, making each stone completely unique.

It forms at low temperatures as silica-rich water seeps into cracks and hollows in sedimentary or volcanic rock and slowly settles into a gel. Australia's opal fields formed this way in ancient inland sea sediments, while Ethiopian and Mexican opal comes from volcanic rock.

Care & Cleansing  +

Spotting a Fake  +

Cool Facts  –

Opal's play of colour comes from tiny silica spheres stacked in a grid that diffracts light like a prism – the spheres are smaller than a wavelength of light.

Most of the world's precious opal comes from Australia, where it is the national gemstone.

Opal can contain up to 20% water, which is why it should never be left somewhere hot and dry.

The Roman writer Pliny tells of a senator named Nonius who chose exile rather than hand his opal over to Mark Antony.

The Science  +