Are Opals Expensive?

Opal is a gem with an infinite number of faces. Every aspect of their appearance has a multitude of potential manifestations. The bodycolor, transparency, and play-of-color of every high-quality stone is unique, while commercial-quality opal has less variation. With so many value characteristics at play, the worth of each and every gem must be tailored to the stone in question. According to the GIA, the process of evaluating an opal entails looking at five separate traits: type, play-of-color, transparency, clarity, and cut.

The Concept of Color is Divided into Two Categories

Unlike many other gemstones whose color can be expressed with just a word or two, the color of opals requires additional explanation. If, for example, someone describes an opal as being red, you don't automatically know if they referring to the bodycolor of the stone or the phenomenal play-of-color expression. Thus, bodycolor and play-of-color are separated into their own categories and described independently from each other.

Background Color/Bodycolor

Background color, also described as bodycolor, refers to the dominant hue(s) of the base stone aside from any phenomenal effect. Professionals sort opals into six categories based on background color. It is important to note that opals are found in only a few places, and deposits only have one or two types present. 

• Black opal - The background color of black opals from Lightning Ridge in Australia can be black, dark gray, green, blue, or brown. However, when illuminated by reflective light, the stone must appear black. These are the rarest of the opal varieties and the best examples are valued higher than any other type. There are three categories of black opal - gray-based, semi-black, and black crystal. The bodycolor of gray-based opal, the least valuable of the three sub-types, is clearly a shade of gray. Semi-black opal is both darker and more transparent than gray-based opal while true black opal is very dark.

• White opal - White opals have a white to medium gray bodycolor that can be yellowish or brownish. The most valuable specimens are a clear white. These are the most numerous of all the opal types and are found in multiple locations, including the United States, Ethiopia, Brazil, and Australia. As they are both common and affordable, this is the type of opal that the general public is most familiar with.

• Crystal opal - This opal type doesn't really have a noticeable background color and can be found alongside other opal types including black opal. It has exceptional transparency and play-of-color which will be addressed below.
• Water opal - Water opals, also called "jelly opals", are similar to crystal opals, but have murkier transparency and inferior play-of-color. These are low-cost gems. 
• Boulder opal - Boulder opals are the opposite of the transparent crystal opals. These gems mined in northeastern Australia in the Winston region of Queensland contain fragments of their opaque host rock which is called a "matrix". This matrixing may consist of a dark brown ironstone or a tan-colored sandstone. A benefit of cutting an opal to include some of the host rock is that it makes the gem much more durable. The matrixing acts as an internal support system to reinforce the notoriously soft gem.

• Fire opal - Unlike the other opal types, the value of fire opals is most dependent on the bodycolor. Almost all fire opals come from Mexico and exhibit a bright red, yellow, or orange background. The most valuable colors are a pure red or combination of red and orange and should be uniformly expressed across the stone.

Play-of-color

Play-of-color is the phenomenal effect exhibited by opals. It describes the flashes of pure spectral color that appear and disappear as the stone moves, and the brighter the better. The play-of-color in individual stones may be a single hue or a dynamic rainbow of many different colors. Typically, flashes of red, yellow, and orange fetch the highest prices while gems that show violet, blue, and green colors are more affordable.

There are two variables associated with play-of-color that contribute to value: the ratio of play-of-color to background color and the quality of the effect. The general rule is that the more play-of-color that shows the full spectrum of hues, the higher the value of the opal. The best opals will show play-of-color with multiple hues when viewed from any direction. 

The pattern of play-of-color expression also impacts value, and buyers prize gems whose phenomenal effects are well balanced across the stone. There are four general categories of play-of-color patterns: pinfire, flash, harlequin, and peacock. The pinfire pattern looks like many tiny spots of color grouped closely together. Alternatively, the flash pattern is characterized by large areas of play-of-color that light up as one unit. The rarest pattern is the harlequin arrangement. It has large patches of color, often of a roughly rectangular shape with well-defined borders, that fit against each other like puzzle pieces. The peacock pattern describes play-of-color that exhibits only blue and green hues.

Play-of-color is most noticeable in high-quality black opal due to the contrast of the dark bodycolor and the bright spectral flashes. White opal and crystal opal can also show exceptional displays of play-of-color. The contrast of dancing play-of-color against solid matrixing makes boulder opal a particularly dynamic gem. Since cutters are not bound to isolate pure opal (which might be isolated in very small pockets), they cut to maximize the visual effect. The value of water opals is lower than other types because they show minimal, or even a complete lack, of play-of-color. 

Fire opals valued for the quality of their bodycolor are the exception to the rule. The presence of play-of-color can be a bonus, but is not required for gems to be considered fine-quality. 

Desirability of Clarity, Expression and Transparency Depends on the Type of Opal

The clarity range for opals spans from entirely transparent to fully opaque. In the end, the most valuable clarity for any type is what enhances the appearance of play-of-color expression best. What looks most beautiful contrasted against one color may not be as attractive against a different background. 

Opaque clarity for black opals highlights the stark play-of-color effect. Similarly, opaque or semi-translucent clarity looks best when it comes to white opal. The best crystal opal is transparent with play-of-color sparkling from inside the gem, while water opals are markedly more cloudy. Only boulder opals should have any opaque host rock visible. Fire opals can be transparent to translucent, but a combination of bright bodycolor with high transparency is valued the highest.

Crazing is Detrimental to Value

Opals are made of tiny silica beads that are loosely packed together. This unique structure is quite porous and can trap large amounts of water - some gems are up to 20% liquid. Unfortunately, the water can also evaporate out of the gem, leading to the formation of a network of internal cracks. This clarity feature is called "crazing", and it is something that you want to avoid. In addition to being unattractive, their presence means that the structural integrity stone is compromised. 

Opals are Often Cut Freeform

Opals grow in small and irregularly shaped gaps and fissures in the ground. This forces cutters to be creative with the gem and polish it to maximize both size and appearance. As a result, most high-value opals are not cut to calibrated proportions. To heighten the uniqueness of fine specimens, cutters will simply polish the stone and leave it in an abstract freeform shape. Alternatively, low-quality opal that doesn't have high-grade qualities to highlight are more likely to be cut into cabochons with standard measurements.

This variation means that there is no standard guide that directly connects cut and value. Instead, cuts that maximize the value characteristics discussed above achieve the highest prices. Size also contributes to the ultimate worth of a gem, with larger examples being much more expensive than tiny wedges.