WHAT IS AN OPAL?

CHARACTERISTICS THAT DETERMINE OPAL VALUE

Specific characteristics are used world wide in determining the price range (value) of opal. The following list outlines those characteristics that must be assessed in order to determine the value of an opal. For an excellent guide to valuing opal refer to "Opal Identification and Value" by Dr. Paul B. Downing. Unfortunately, this book is presently out of print, try your local library.

TO DETERMINE THE SPECIFIC VALUE OF AN OPAL
Before attempting to determine the specific value of a particular opal one must first classify the opal using four main characteristics listed above "Type of Opal", "Base Color", "Brightness of Color", "Weight". The price range determined using these characteristics is generally quite broad.

Then, use the following characteristics to narrow the price range to a specific price.

Fire Color
Fire refers to the "play of color" emitted by the opal rather than the "base color of the opal" (see page describing base colors). In general, the more red or orange fire colors the higher the value. The brightness of the play of color is very important when valuing opal Ü the brighter the better.

Pattern
Generally speaking, the larger patterns or chunks of fire color are more showy and therefore more valuable. The stone is more valuable if the pattern of fire color moves or rolls when the stone is moved or if alternate colors show when the stone is moved. Harlequin pattern and rolling broadflash fire are the most prized.

Dome
Generally a high is more attractive and thus considered by some to be more valuable. This is more a matter of individual preference. Dome height greatly affects the weight of a stone.

Cut
Irregularly cut stones and stones with pits, scratches or flat spots have a lower value.

Shape
With white and crystal opal the "oval" shape and calibrated sizes are more valuable because settings are more readily available. Freeform pieces are more distinctive and individual but require individual settings that increase costs.

Inclusions
Inclusions in the opal that affect the overall appearance and beauty of a stone have the greatest effect on the price; although any inclusion generally lowers the value.

Cracks
Although acceptable in assembled stones such as doublets and triplets, cracks or crazing in solid opals reduces the quality and value to were it is generally not acceptable for use in jewellery. The value of a cracked or crazed opal is generally valued at 10 to 25% of the value of an otherwise similar "clean" stone.

Consistency
Consistent brightness and pattern in a stone is desirable and optimizes value.

Directionality
The direction (field of view) from which the play of color is visible (particularly the optimum brightness, pattern and fire color) affects the value of an opal. Directionality is difficult to avoid when cutting and is often a particular problem with "broadflash" fire patterns. Price is affected only to the extent that the overall beauty of the stone is affected.

Size
Bigger, although preferred to smaller, has a great effect on price. Stones should not be so large that they become awkward. Generally, very large stones (over 40 carats) are cut into smaller stones. Stones weighing less than 1 carat in weight (less that 8x6 mm. in size) sell at lower prices because they are more readily available. Generally speaking, opal stones seldom exceed 8 to 10 carats in weight (18x13 mm. in size) because larger pieces of opal are more difficult to find.

Rarity
Rarity refers to characteristics such as patterns or pictures apparent in a stone and can also relate to the site from which the opal is mined.