G ems are nature’s masterpieces. Their visual appeal is a result of colour, cut quality, surface appearance and the ability to reflect light. It’s important to understand what makes one gem more valuable than another and how you can choose a perfect gemstone. Here are seven steps to follow when shopping for the perfect coloured stone:

Colour : For every gem variety, colour is the most important value factor. Hue isn’t the only factor that matters in a gem’s colour. A colour’s tone and saturation are also important. Brighter, more vivid colours with a medium tone are generally the most sought after. For example, the most valued green is often a ‘grass green,’ while pale celadon, lime or dark hunter shades may have lower prices. Gems that are very pale, very dark or whose hues are tinged with brown or gray are considered less valuable.

Light Refraction : The colour of different gems is affected by different light sources. For example, blue sapphires are best illuminated by a fluorescent light and rubies under an incandescent light. Gems like alexandrite change colour in different lights. Sapphire and chrysoberyl show patterns such as stars and cat’s eyes when a spotlight is shone on them. Others, like opal exhibit play-of-colour, while moonstones display adularescence, a glow that appears to float over the surface of an otherwise colourless, transparent to semi-transparent gem. Always look at a gem under different light sources before deciding if it’s the right choice.

Clarity : Another important factor of gemstone quality is its clarity or absence of internal characteristics known as inclusions. A majority of gems are the most valuable when they have few inclusions visible to the naked eye. Clarity has the most impact on pastel coloured gems because inclusions are much easier to see when the colour is pale.

Inclusions : A small number gems are considered more beautiful and valuable because of their inclusions. A demantoid garnet, for instance, with a horsetail inclusion is a signature of this rare green garnet. An emerald with a three-phase inclusion (a tiny internal pocket filled with a liquid, a solid crystal and a gas bubble) is characteristic of emeralds mined in Colombia. Amber that contains an ancient insect or inclusions in cat’s eye chrysoberyl and star sapphires give them distinct character. Make sure, however, that inclusions are not located in a corner or on an edge where they might reduce durability.

Carat weight : Gems are sold by weight rather than by size. The measurement used is the carat, which is one-fifth of a gram. Few gems occur in large sizes. Among these are emerald, ruby, sapphire, tsavorite garnet, alexandrite and spinel. For these gems in particular, you can expect to pay much more per carat for a large stone than you would for a small one. Gems like amethyst, citrine, blue topaz and amber are more available in large sizes so these gems may have a similar price per carat as smaller stones. A one-carat Emerald and a one-carat Ruby are the same weight but not the same size because each is a different mineral with a different density. This difference in density can be used to help identify gems too.

Cut and beauty : It’s the skilled hand of the gem cutter that unleashes a gemstone’s brilliance and beauty. Each gem handles light differently due to the unique optical properties of its crystal structure. When discussing cut, it refers to two things: the three-dimensional shape in which the gemstone is fashioned (round brilliant, oval, emerald cut, etc.) and the cut quality. In other words, how well the gems shape delivers brilliance and beauty. To evaluate a cut, look at how the gem returns light to the eye. The best cuts are symmetrical and return light across the entire surface of the ge, with no dark or washed out areas.

Keep these factors in mind when shopping for a coloured gemstone, and be sure to ask for a GIA Colored Stone report to verify its authenticity and characteristics.

GIA is recognized as the world’s foremost authority in gemmology. The creator of the famous 4Cs (Colour, Cut, Clarity and Carat weight) of diamond quality, GIA is a global public benefit institute with a mission to ensure the public trust in gems and jewellery through research, education, laboratory services and instrument development. The Institute upholds the highest standards of integrity, academics, science, and professionalism.

INTERNATIONAL FOOTPRINT

While the Institute operates in many countries and speaks many languages, GIA’s mission is a strong grading services, the Institute is entrusted with grading and identifying more gems than any other lab and has graded some of the world’s most famous gems including the Hope Diamond and the Taylor-Burton.

GIA EDUCATION

Over the course of its 83-plus years, the Institute has educated more than 350,000 professionals worldwide. The GIA Graduate Gemologist diploma program, which focuses on gem grading and identification, is the industry’s highest professional credential. GIA also offers training geared to every sector of the industry with its Graduate Jeweler, Accredited Jewelry Professional and other diploma programs.

GIA LABORATORY

Staffed by expert diamond graders and gemmologists, GIA laboratories set the standard for grading and identification practices worldwide. Known for its strict impartiality and benchmarkgrading services, the Institute is entrusted with grading and identifying more gems than any other lab and has graded some of the world’s most famous gems including the Hope Diamond and the Taylor-Burton.