Sapphire and Diamond Engagement Ring.

You can start by trusting your own personal instincts. Sensory appeal is always paramount. So, if a particular gem or jewellery design “speaks” to you, by all means listen!

You can also use what you know about the Diamond 4Cs. The familiar diamond characteristics and value factors of colour, cut, clarity, and carat weight also can be applied to coloured gems as well. However, each coloured gem variety is judged by its own potential: no one expects an aquamarine to have the same blue colour as a sapphire or an emerald to be as flawless and clean as an aquamarine. But there are a few general rules you can use to judge any coloured gemstone quality

Every gem has a unique range of colours. Generally speaking, the purest and most vivid colour a gemstone can have will also be the most rare, desirable and therefore expensive. But to really explain gemstone colour, we need to look at the three factors that define any gemstones colour.

The first is its hue, which is what we normally regard as colour: for example, a gem's hue will be red, orange, yellow, green, blue, or purple, or it might be in-between two hues: an orangey red or a reddish orange. For most gem varieties, a pure hue is most favored. Gems with a pure red, blue, or green hue are generally the most favored of all.

The second factor is saturation, the intensity of the colour. This is the tricky one to picture. Colours that lack intensity often appear faded or washed out or look as though the hue is mixed with gray or brown. A fire engine red is highly saturated, a brick red less so. In gemstone colour, more saturation is always better.

The third factor is tone, the lightness of darkness of the colour. Pink has a light tone and maroon has a dark tone. In gems, a medium tone, not too light but not too dark, is considered best. Too light, and a gem's colour is too pale to be attractive. Too dark, and a gem isn't able to sparkle with light.

A gem's colour is evaluated for hue, saturation and tone. For example, the best rubies have a vivid pure red colour in a medium tone, with no modifying purple, orange, or brown.

But each gem variety is judged on its own terms. For example, aquamarine always has a fairly light tone but its lightness is part of its watery appeal. Gems like orange-pink Padparadscha sapphire or blue green Paraiba tourmaline are so beautiful, they make gem dealers forget that pure hues are supposed to be better than mixed ones. These gems sell for premium prices simply because almost everyone finds them beautiful. So feel free to follow your own taste.

Next to colour, cut is the most important factor in beauty. Faceted gemstones should have a pleasing shape with a lively display of colour and light. The flashes of brilliance a beautiful gem displays are thanks to the skill of the cutter, who selects just the right orientation and angles and proportions to maximize a gem’s appeal.

How can you tell if a gem is well cut? First, it should display brilliance and scintillation evenly across the face of the gem. Unlike diamonds, there is no “ideal” set of proportions for cut: since each variety is different optically, it requires different angles and ratios to look its best.

Move the gem around and see how it handles light. There shouldn’t be any dark lifeless areas or flat washed out zones: light should be reflected consistently back to the eye. Poorly cut gems may have a window: a non-sparkling area in the center where light just shines through the back instead of being reflected back to dazzle your eye. You’ll find that close observation will reveal whether a gem dances with light or just sits there.

coloured gemstones have much more variety in cuts and shapes available than ever before. Standard ovals, rounds, cushions, trillions, emerald cuts, princess cuts, pears, and marquise shapes have been joined by even more options, traditional and new. Opals, chalcedony, cat’s-eyes, star sapphires, laps, coral, turquoise, and other gems with rich deep colour are often cut in the smooth dome shape called the cabochon, the favorite shape of the ancient world, which emphasizes colour over brilliance.

In addition to standard shapes, the work of today’s innovative lapidary artists also adds unique possibilities to one of a kind jewelry with unusual new shapes and faceting styles.

All natural gemstones have characteristic inclusions that form along with the gem in the earth. These inclusions may be crystals, needles, voids, fissures, or even tiny pockets of liquid trapped inside. If they don’t detract from appearance, clarity features are accepted in most coloured gems and don’t affect value. In fact, they provide a benefit by proving that the gem is natural.

Still, the ideal for most gems is that there should be no inclusions readily visible with the naked eye, particularly if the gem has a light colour. There are some gemstones that are extremely rare without visible inclusions. You should expect to see inclusions in emerald, red tourmaline, and, to a lesser extent, ruby.

Most coloured gems are available in a wide range of sizes, but for some the selection is limited. Gems are generally sold by weight, using the carat, which is one-fifth of a gram. Some gem varieties are more dense than others: a one carat emerald will be noticeably larger in size than a one-carat sapphire or ruby. In general, the larger the gem, the more expensive it will be per carat.

For the classic gems like ruby, emerald, and sapphire, prices per carat can increase dramatically as sizes increase. For example, since large ruby is very rare, a three-carat ruby might be three times the price per carat of a one-carat ruby, or nine times the total price.

Some gems are much more available in large sizes so the price doesn't rise as much as the size goes up. Amethyst, Citrine, Aquamarine, Tanzanite, and Tourmaline might have similar prices per carat for a one-carat and a ten-carat stone; although the ten-carat stone will, of course, still be ten times the price.

In addition to the 4Cs, gem values are influenced by natural rarity and the economics of supply and demand. This explains why gems that look similar in colour and size can differ substantially in price.

Both sides of the equation of supply and demand come into play. Alexandrite, rare but in demand from collectors, may cost as much as better-known gems. Some gems are relatively rare but since they aren’t well known, there is little demand, keeping prices low. The ancient world couldn’t tell ruby and spinel apart, but spinel’s role as an unknown understudy keeps its price relatively low today even though a one-carat red spinel is more rare than a one-carat ruby. Other rare gems that are relatively affordable include tsavorite garnet, morganite, red beryl, and zircon.

Within each gem variety, quality determines cost. But different gem varieties have different pricing structures. In general, classic ruby, blue sapphire, and emerald are the most expensive gemstones. One level below these are the rare collector’s gems like alexandrite, demantoid garnet, Paraiba tourmaline, black opal, pink topaz, jadeite, chrysoberyl cat’s eye, fancy sapphire and South Sea cultured pearls. The moderate price range includes tanzanite, tsavorite garnet, tourmaline, red spinel, aquamarine, precious topaz, spessartite garnet, and Tahitian cultured pearls. Affordable gemstones include amethyst, citrine, spinel, many colours of garnet, blue topaz, chrome diopside, fire opal, white opal, iolite, kuzite, peridot, coral, turquoise, lapis lazuli, chalcedony, and freshwater and saltwater cultured pearls.

The creativity and craftsmanship that go into fashioning gems and making jewellery also affect the va\lue of the finished product. Besides being beautiful, an exquisite gem reflects the union of aesthetics, science, and technical mastery. Fine jewellery combines gems and precious metal with talented design, skilled execution, and attention to even the smallest details.

Value isn't a deep or complex mystery. However, it simply makes sense to have the guidance of a professional you trust when you purchase your coloured gemstone jewellery.

At Daniel Prince we can show you how to judge a gemstone's quality. our gemmologist has the knowledge and training to give you good advice about choosing gems and pearls, with full disclosure of all the facts that are needed to make an educated and satisfying purchase decision. Just as important, we're passionate about sharing the beauty and wonder of natural coloured gemstones and cultured pearls.