Determining the Value of a Gemstone: Sapphires, Tsavorites, Tourmalines and More.
Precious and semi-precious gemstone’s are fantastic stones to use in fine jewellery. They offer a vibrant color palette and a unique aesthetic to the designs they are placed into. Much like diamonds, there is a specific way in which these stones are valued. Determining the value of a gemstone comes down to factors such as color, cut, clarity, carat, as well as the rarity, hardness and pureness of the stones.
For a deep dive into the topic, download Anpé’s full Determining a Value of a Gemstone guide here!
Color is one of the most important factors when determining the value of a colored gemstone. Gem cutters cut gemstones in a way that enhances and emphasises the best qualities of that individual stone, such as its luster, fire, and luminescence. Cutting them in a way that accentuates its natural color makes the stone more valuable.
There are four important elements that make up gemstone color:
Hue, saturation, tone and coverage.
Hue is the initial color of the stone. Sapphires, for example, come in virtually any color or tone you can think of. Some colors are more valuable than others, such as bi-color and color changing sapphires.
Coverage simply refers to the consistency and evenness of color throughout the stone.
Saturation is a stone’s brightness and intensity. This can range from dull to vivid. The more vibrant and saturated the stone, the higher the value.
A gem’s tone is the depth of color present within the stone, ranging from light to dark. Both light and dark tones of the same stone can have an equal value to each other.
A gemstone’s clarity grade refers to the relative absence of inclusions, fractures, and blemishes that affect its appearance and structural integrity. These inclusions and blemishes are materials that are trapped inside the gem as well as surface imperfections, both of which vary due to the many ways gemstones form underground.
Gems with greater clarity are considered more valuable than gems of the same species with lower clarity, all other properties being equal.
That being said, some inclusions can have positive effects, by bringing a unique aura to the stone.
One of the major exceptions to the rule of clarity comes about with emerald stones. Emeralds are incredibly prized throughout different cultures, but they are one of the gemstones that always occur with hints of other mineral traces in them. This is why you will see highly prized emeralds with some inclusions and flaws.
Gem cutters, also known as lapidaries, have a massive artistic ability, as they take rough gemstones (see image) and hand cut them into the sparkling beauties you see mounted in a finished design.
A quality cut takes the other Four C’s into account and enhances the stone’s best features, such as the hue, saturation and color tone. A professional lapidary will be able to look at an individual gemstone and be able to determine the best angles to cut to bring out the stone’s inherent beauty – and in doing so, bring it the most value.
All gemstones have a unique way in which they bend light (refraction) and bounce it to your eye (reflection), which is what makes them so eye catching.
Gem cutters have an incredible way of creating facets and surfaces that optimise the quality of light that passes through each gemstone into your eyes.
The size of a gemstone is generally measured by weight in the metric known as carats (1 carat is equal to 1/5 of a gram). Traditionally, when purchasing a loose gem, the cost is given as a per-carat price and as the weight of a carat increases, so does the cost.
Unfortunately, prices are not “set in stone”. For example, the cost of a 1ct. sapphire will not equally double if you have a 2ct. sapphire. This is because larger stones are typically rarer in nature. The rarer the stone, the more desirable and expensive it becomes.
Milestone Carat Weights, otherwise known as “magic sizes,” are quarter sizes of diamonds, such as .25ct, .50ct, 1ct, etc. These popular sizes are generally easier to refer to, therefore making them higher in demand. But what is so “magical” about them? Well, the price magically jumps once a stone reaches the next quarter carat.
Rarity is one of the most prized qualities of gemstones and is another major factor that determines the price for different minerals. Gemstones that are produced in fewer regions across the world in smaller quantities are generally worth more.
For example, finding a padparadscha sapphire over the weight of 2 carats is a real rarity, and can even surpass the price of a diamond in similar size.
Gemstones, just like other products and resources, have a supply and demand relationship. For example, the most common gem-grade corundum is the blue sapphire. Sapphires come in all the colors of the rainbow, with certain colors rarer than blues. This might make you wonder why blue sapphires are so valuable, and the answer is because traditionally, many people desire deep blue sapphires over yellow or green ones. It is that exact demand that drives up the price of blue sapphires.
Hardness refers to the durability of your gemstone. More importantly, it measures how difficult or easy it is to scratch the surface of the stone. The hardness of a gemstone is measured using the Mohs Scale of Hardness, rated on a scale from 1 to 10.
The reason this is important to determining a gemstone’s value is because specific minerals may not interact positively with the environment around you.
For example, diamond and corundum (sapphires and rubies) rank highest on the scale, between 9 and 10. This means that these gemstones are resilient and great for everyday wear, so long as you take care of them properly. A calcite or fluorite gemstone, however, ranks 3 to 4 on the scale, meaning they scratch fairly easily, thus making the appearance seem dull and used after a time. Ultimately, the higher up on the Mohs Scale, the higher the value of the stone.
Gemstones are altered as soon as they come from the ground in their rough form and are cut and polished to become the wonderful stones we see in our jewellery today. But there are a number of treatments that are used to change the color and clarity of a gemstone.
Heating and oiling are common treatments to artificially change and improve the color and clarity of stones.
When a gemstone is noted as “unheated”, this means that the color and clarity are completely natural. Untreated stones are often of higher value because they are less common within the industry. In the image on the side is a natural, unheated bi color sapphire, which is incredibly rare in nature.
A vast majority of the stones from Anpé Atelier are unheated and a professional certificate is always provided which gives information on what exactly has or has not been done to the gemstone.