Black opals are the most valued of all opals mined in Australia. The rarity of this particular gem has caused its price to increase dramatically in recent years. After all, most of the world's supply of black opals comes from one small mining town.

Origins of Black opals

Lightening Ridge is a small town, in New South Wales, about 10 hours from the Gold Coast (give time north-west of Sydney). Over the years, millions of dollars worth of black opals have been mined in Lightening Ridge. Mintabie in South Australia is another source of black opals.

The first record of a black opal found in Lightening Ridge goes back to 1873, but it was not until 1903 that people realized how valuable this gemstone was. Black opals mined in Lightening Ridge changed the market value of opals and set a new precedent for the gem.

Characteristics of a Black Opal

The main characteristic of a black opal is a dark body, ranging from dark gray to soot black. The body tone is only a general characteristic and is in no way related to the spectral or rainbow colours in the gem. Many people think that a black opal is completely black in colour. If it was so, it would have been totally worthless.

The dark body tone of the opal is caused by traces of iron oxide and carbon. The dark tone is an advantage because it ensures that the rainbow colours in the opal stand out. The contrast of the body tone against the fire colour makes black opals highly desirable and increases their prices.

Cutting a Black Opal

Gem cutters will usually leave a layer of potch (common opal) behind the stone, which enhances the dark tone of the gem and lends it extra vibrancy. The darker the colour of the potch backing, darker is the body tone of the stone. Triplets and doublets, which imitate black opals, are based on this principle.

Most black opals are cut into oval shapes, but the shape also depends on the stone's natural shape. as a result opals are also cut into teardrop or free-form shapes to maximize the carat weight and size of the gem.

It is not necessary that a black opal should fetch a high price. There are other factors such as the pattern's uniqueness, brightness, cabochon shape, and the color of the pattern (the most valuable pattern colour in a black opal is red, but green and orange fire colors are also good for investment) which affect the price of a black opal.