Opal Buying Guide For Jewelry

Buying loose opal online can be a very confusing experience for many first time or beginner buyers. First, a buyer should understand the most basic categories which opals can be divided. These include Solid Opal, Doublets, Triplets, Treated, and Synthetic opal. These basic categories are described below:

how to buy loose opals online for jewelryAn Opal Buying Guide For Loose Opals

  1. Solid Opal - A 100% natural stone, cut and polished. These stones normally are natural opal, showing color, formed on a host rock. A completed stone will include the host rock left as the backing of the stone with the face showing color. A subsection of Solid Opals is that of Solid Crystal Opal. These opals show color all the way through the opal, 360 degrees, and can range from Light to Black Opals. See below for more information.

  2. Opal Doublet – A thin piece of natural clear crystal opal showing color is glued to a piece of natural black potch (common opal showing no color) or iron stone (the base of boulder opal). This combination is then cut and polished. These stones can show excellent color due to the black background added and are considerably cheaper. Glue cannot be seen through the opals face because of a black layer of paint applied directly to the opal sliver, which looks natural. The domes of these stones are low to flat. Commonly used in bezel settings by jewelers. Order of construction from face to base is: Opal sliver, black paint, glue, backing.

  3. Triplet Opal – A very thin sliver of opal is glued to a black background and a large quarts or glass dome is placed on top of opal sliver. This creates beautiful bright stones that are accented by the dome, allowing color to be shown brilliantly at most angles.

  4. Treated Opal – These opals are treated to enhance the color of the stone. Most commonly treated is Opal matrix from Andamooka Australia. A naturally porous white opal that is treated to turn the stone black. This process brings out the color dramatically. Stones are cooked in sulfuric acid and sugar in this treatment process.

  5. Synthetic Opal – White Lab created opal showing color. Pattern of color is differs from natural opal. Can be cut into thin slivers used in triplets or cut as solids.

The next thing a buyer should consider is Body Tone. Body tone is the color that an opal appears when the flash of an opal’s color is not being shown. Body tone is separated into Light, Dark, or Black Opal. Light opal is commonly called white opal and Dark opal is commonly called Semi-Black opal. A scale is used to name the Body tone of an opal. This scale ranges from N9 to N1, where N9 is a pure white and N1 is a pure black. This scale can be found on most sellers’ pages. When buying opal online, be sure to compare the opal body tone listed by the seller to the pictures taken of the stone. Sometimes photos will make an opal appear a shade or two off their actual body tone. The seller’s listed body tone should be the definitive word as it is his or her responsibility to list the correct body tone. Black opal is the most rare and valuable opal.

Next, the Brightness of all opals is rated on a scale from 1-5, with 5 being gem bright. Very few stones can be rated at a brightness of 5. A rating of 3 represents the average brightness of opal. The best way to judge the brightness of an opal is to use direct sunlight around noon. Be sure to try multiple light sources to find when your opal will display its color best. When buying online, look for striations (lines) in the color flecks. This is normally a good indicator of a 4+ bright stone.

The Transparency of an opal describes how light penetrates the stone. Opaque stones do not let any light pass through, such as black opal that was formed on potch. Translucent opal lets some light penetrate, but not entirely through the stone. If you can see a depth into the stone’s face, but cannot see your finger behind it, you have a translucent stone. Transparent stones let light pass all the way though the stone, such as clear crystal opal.

The Outline shape describes the shape of the opal when looking directly down at the opal’s face. The most valuable and desired shape is the oval. However, a Freeform shape is very common with opal. Freeform stones do not have a set outline as the name suggest. It is a general rule that the most attractive Freeform stones have the fewest number of sides possible and do not have sharp corners. Another popular outline is a tear drop shape or marquis shape. Opal can be carved or have undulating faces as well. See “profile” right below for more information on undulated faces.

The Profile of an opal describes the appearance of an opal’s face when looking at the stone directly from the side. A cabochon shape describes a stone with a dome. Faceted stones consists of many flat faces, such as the way diamonds, rubies, and sapphires are cut. Opals typically are cut as cabochons. These Cabochons can have high, medium, or low domes. High domes make a stone more valuable. Opals may also have a flat face or an undulating face. An undulated face appears as rolling hills but in reverse, such as rolling valleys. Opals can also be faceted. Mexican opals and Ethiopian crystals are commonly cut as faceted stones.

The Origin of a stone is important to the general appearance of any opal. By knowing the origin, a buyer can be familiar with a stone online in seconds without having to guess. Every location where opal is found is cut to a unique style attributed to that location. For instance, Lighting Ridge opal is usually cut with a domed back. Opals are found in many places in the world. However, Lightning Ridge is the most famous, valuable, and beautiful of all opal.

The Pattern of an opal describes how an opal flashes in light. Most opals are a mixed pattern. The pattern of color can make an opal more valuable or less depending on the pattern type. A Pinfire pattern decreases the value per carat of an opal whereas a “named pattern” will increase the value. A Ribbon pattern stone is a good example of a named pattern type stone. Many sellers offer videos to show the many different patterns.

The Display of an opal describes the angles at which an opal shows color. A strong stone shows color at all angles when looking directly at the face. The display of a stone is judged by looking directly at the opal’s face and rotating the stone a quarter of a turn four times, making one complete rotation similar to a clock’s movement. Look for sellers that show their stones at as many angles of rotation possible for the most accurate idea of what you are buying. Many buyers overlook this as they pay more for stones than necessary because the seller shot seven pictures total, showing only the two best angles of display.

opal online

Inclusions are the impurities that can be seen on or through the face of an opal. These can be sand spots or potch that meets the face. Unfortunately inclusions are can be found on some opals, but do not count all of these stones out. Boulder Opal commonly has inclusions and is very valuable. An inclusion lowers the price per carat of a stone, how much depends on the percentage of the inclusions surface area compared to that of the entire face. An inclusion of 5% or less does not dramatically reduce the price of a stone.

Finally, Carat Weight is an important factor of buying opal. Commercial stones are normally between 2-5 carats in weight and are the most desired by jewellers. A stone of the exact same quality in color, body tone, flash, brightness, etc., will be less valuable per carat if the stone is too large or too small.

These are the main factors to consider when purchasing a loose opal. Check out all of Thank you for looking and considering opals.

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20 people found this article helpful



Very informative.

4th Dec 2019

Excellent information. Thank you for sharing.

10th Nov 2018

very good, very clear explaining. Help me a lot.

18th Apr 2017

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