How to Choose Gemstones and Jewellery

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Gemstones are prized for their beauty, durability and rarity. Some are organic, such as pearls and amber, while others are inorganic, such as agates and rubies.

Color

Color is an important factor in determining the value of gems. The most valuable gemstones are those with intense hues that are sought after by consumers; these include rubies, sapphires (especially in a blue variety known as sapphire), green garnets (including tsavorite and demantoid), malaya and star garnets, and padparadscha tourmaline.

Most gemstones acquire their colors due to a combination of chemical and physical factors. The most common cause is the presence of dispersed metal ions in the crystal structure; for example, rubies and sapphires are both made from corundum, and their bright colors come from a combination of iron and titanium ions.

Occasionally, a gem can be colorless because the metals are not present in the proper concentrations. This is often the case with clear quartz, amethyst, chalcedony, and some citrines.

While natural colours are desirable, some gems also gain their colour through other methods. These can be as subtle as adding oxides to a gem to alter its hue or as dramatic as changing its light behaviour, as with the spectacular pleochroism of kiwi green to reddish pink tones in Turkey’s diaspore or in moldavite from Australia’s Lightning Ridge.

Colour changes have captivated mankind for centuries, whether as the calming flashes of Opal or as the Victorian practice of wearing gems whose first letters lined up to spell words like ‘dear’ and ‘adored’ (acrostic jewellery). For those who are fascinated by these fascinating stones, a look at some of the most beautiful synthetic and treated gemstones in the world can be eye-opening.

Clarity

Gemstones have a variety of natural features that are related to their clarity and inclusions. When selecting a gemstone, you will want to look for those that are free from these inclusions as much as possible. However, it is also important to remember that different gems have their own tolerance levels for these inclusions. For instance, a transparent ruby can be more forgiving than an emerald when it comes to inclusions.

Clarity is a very important factor in determining the value of a gemstone. It refers to the gemstone’s ability to be clear or translucent, which allows light to pass through. A gem with excellent clarity is flawless and will be able to reflect more light, which increases the brilliance of the gemstone.

While a beautiful color is the most important feature in determining the price of a gemstone, clarity is still important because inclusions can affect the durability of a gem. The inclusions in a gem are judged on their nature, size, number, position and relief.

Gemstones are often graded with letters and numbers such as VVS, VS and SI. These represent the gemological institute of America’s (GIA) clarity grading codes, which jewelers and gemologists use to determine the clarity of a gemstone. The grading system considers the visibility of inclusions, their impact on the gemstone’s appearance and durability, and the extent to which they interfere with a stone’s transparency.

Carat Weight

Carat weight is a measure of the size and value of gemstones and diamonds. One carat is equal to 200 milligrams (0.002 ounces). Gemstone sizes are often described by their carat weight, but the size of a stone can differ from its carat weight depending on how the gem was cut. This is because gem cutters usually aim to make diamonds of ideal proportions, but many colored gems are cut into larger volumes than diamonds, which can reduce their actual weight.

The term carat is derived from the ancient practice of using carob seeds, or keration in Greek and Qirrat in Arabic, as counterweights to balance scales used for precious metals and gemstones. They were chosen for this purpose because they are uniform in size and have consistent weights, making them a reliable unit of measurement. It wasn’t until 1907 that the metric carat was adopted at the Fourth General Conference on Weights and Measures as the standard measurement for diamond and gemstone weights.

Carat weight is distinct from karat, which is the unit of measurement used for gold and its alloys. Some jewelry sellers use the terms interchangeably, but they have very different meanings. Karat refers to the purity of gold, while carat relates to gemstone weight. When purchasing jewellery, it is important to understand the differences between these two measurements.

Cut

When choosing gems, it’s important to think about both shape and cut. While shape describes the outer shape of the gem, cut refers to how facets are arranged to maximize the stone’s colour and clarity. A skilled gem cutter will be able to turn fine rough stones into sparkling baubles through a meticulous process called faceting.

The most popular gem cuts include the round brilliant, princess, and emerald. Round brilliant cuts are designed to give a gemstone its most scintillation (sparkle), while princess cuts are more subtle. Emerald cuts, on the other hand, offer a more refined look and are a good choice for delicate jewellery pieces.

There are many different variations of these classic shapes, too. Trilliant, kite, hexagon and baguette cuts, for example, are a bit more unique and tend to work well with translucent gems like citrines or amethysts. Another alternative is the Asscher cut, which combines a princess and an emerald cut to create a recognizable “X” shape.

For something really special, consider a marquise cut, which is similar to a triangle shape but with the added benefit of perfect symmetry between two ends of the gemstone. A Portuguese cut, on the other hand, features a mixture of step and brilliant facets to offer a more complex, three-dimensional effect.