Are opals rated by A, B, C etc. What determines best quality?

Question

Specifically interested in Black Australian Opals.

Answer 1

The value of an opal depends on many factors. The type of opal, body tone, brilliance, pattern, colour bar thickness, the play of colour, and faults all play important roles in determining the value.

Other important factors include the quality of the cut & polish, and the size of the stone. When being valued, opal is carefully examined and given a price 'per carat'. The overall carat size of the stone will then determine the price of the opal.

Truth be known, there is no standardised or set method for valuing opals, as each opal is extremely unique in terms of pattern, brightness, and colouring (unlike diamonds, which can be more accurately valued according to a set chart of colours, clarity, faults, etc.) Always ask for a certificate of valuation / authenticity with your opal, and get a second opinion from an experienced valuer if you are concerned about the value of your stone.

The finest BLACK OPAL in the world comes from Lightning Ridge Australia in New South Wales. It is the RAREST of all opals and can sell for millions of dollars or more. The Red Multicolored form of black opal is the most prized !

Answer 2

Don't understand your question? But if you Google in-Gooberpedy you might find your answer.This is the most famous opal town in Australia.

Answer 3

I think that your question is related to the way in which the colour of diamonds is graded (in fact diamonds start at D and work their way down from there).

If my assumption is right the answer to your question is NO opals are not colour graded in this way at all. The grading of opals is carried out using the graders experience. There is no fixed scale and each opal is assessed purely on the total beauty  of its appearance.

The only colour grades that are used are very rough categories such as black, semi-black, grey, crystal etc.