The body tone of an opal is different to the play-of-colour displayed in precious opal. Body tone refers to the relative darkness or lightness of the opal when ignoring the play-of-colour.

Black Opal - is the family of opal which shows a play-of-colour within or on a black body tone N1, N2, N3 and N4 are viewed as black opal.

Dark Opal - is the family of opal which shows a play-of-colour within or on a dark body tone, N5, N6 are viewed as dark opal or semi-black opal.

Light Opal - is the family of opal which shows a play-of-colour within or on a light body tone N7 and N8 are viewed as light opal. The N9  category is viewed  as white opal.

Opal with a distinct coloured body (such as yellow, orange, red or brown) should be classified as black, dark or light opal with a notation stating its colour hue.

The brightness of the colour is the most critical when assessing the value of opal. Red is the most sort after colour, followed by orange, gold, green, blue & violet.  Therefore red opal is generally more valuable than a predominantly green opal, which in turn is more valuable than a stone showing only blue colour. However, brilliance, darkness & pattern are the main decision makers - a brilliant blue/green can cost more than a dull red; bright twinkling stars of a 'pinfire' pattern can cost more than a cloudy open pattern of similar colouration; or a brilliant, lustrous light opal can cost more than a lacklustre black opal.

The type, colour, size and soundness of precious opal are factors that determine the price paid for the gemstone. The price is based on the quality of the opal and expressed per carat. Furthermore, there is a marked difference between the value of uncut opal compared with the value of cut and polished opal.

Pattern Almost all opal displays some form of pattern. You will never find two opals that are the same. In particular, many of the top quality pieces of black boulder opal show their strength through a distinct recognizable pattern play of strong colours. Some of the various patterns are listed below.

Harlequin is extremely rare and the most prized pattern, this consists of the colour pattern resembling a near perfect checker board.

Floral is possibly the most common of all patterns as it covers a broad range of shapes & designs , some what like the floral pattern on a ladies dress.

Pinfire is the arrangment of colour with the appearance of stars or small dots in the stone.

Brush Strokes some what resembles a painters pallet with the large odd shaped blotches of different colours.

Rolling Flash is more common where one predominate colour travels across the stone as it is moved.

Background Colour It is important to know the type of opal. Solid precious opal is much more valuable than doublet or triplet opals, doublets or triplets are NOT SOLID NATURAL OPALS & HAVE NEAR NO VALUE. Black  boulder opal is more valuble than semi-black, which in turnis more valuable than light opal. The darker the body colour, the more valuable the gem.