Black opals are hard to come across as they are only known to develop in one location: Australia. In fact, the town of Lightning Ridge produces the majority of the opals discovered on the continent. But what exactly are black opals and why are they so precious?
What are black opals?
So what gives black opals their distinguishable hue? Black opals are formed from is layers of hydrated silica with a water content ranging from 6% to 21%. The stacks form a perfect cubic structure that diffracts light and emits a flaming display of bright hues, which we call "play of colour."
Black Opal Appearance
Black opals, unlike more common opals, contain trace quantities of carbon and iron oxide, which contribute to the stone's remarkable blackness. The rainbow colours in a black opal shine out considerably stronger than in lighter opals due to their dark body tone.
Because of its vibrant colour, black opal is the most precious of all opals. A natural coating of potch (colourless opal) is frequently left on the back of a black opal, which can provide more blackness and brightness to the stone. The deeper the potch backing, the darker the body tone, which typically results in more colour vibrancy and a higher black opal rating.
The rarity of black opal gemstones
The remarkable colour combinations and patterns of black opal make it one of the most valuable forms of opal. While black opal is plentiful in the gemstone market, high-quality black opal is uncommon due to the stone's strong colour contrast between the dark body tone and rainbow flashes that gleam beautifully throughout the gemstone.