Your Guide to Coloured Gemstones

Coloured stones are having a moment – but with many gems to choose from, deciding what coloured stone jewellery to invest in might seem like a daunting task. Let’s start with the basics.

What’s in a name?

It may surprise you to know there are only two classifications of gem: precious gemstones and gemstones.

The four precious stones are well known; diamond, emerald, ruby and sapphire. Other stones are often known by the term ‘semi-precious’, but it’s an outdated and inaccurate way of referring to these gems. 

Because while ‘semi-precious’ suggests an inferior stone, many gemstones not classed as ‘precious’ can be incredibly valuable. Indeed, the second most expensive stone in the world is a jadeite, auctioned at an incredible US$3 million (approximately HK$23.5 million) per carat. 

Diamond, emerald, ruby and sapphire are fine jewellery classics, and have earned the historical prestige and reputation to be known as precious stones.

And those other stones? For these, you can simply say ‘gemstones’ or ‘gems’ – and all are special in their own way.

What influences a coloured gemstone’s value?

Like diamonds, coloured stones are graded by carat, cut, clarity and colour.

Carat is a measure of the weight of the stone – a one carat stone would be written as 1.00ct - equal to 0.20g in weight.

Traditionally, gem prices are always given as per carat price. The price per carat generally increases as a stone gets larger.

The rate at which the price increases with weight differs from one kind of gem to another, and prices are influenced mainly by rarity and demand.

Cut refers to both the shape of the stone and how well it has been cut. A skilled gem-cutter, or lapidarist, will cut the stone to best show off its unique properties and colour. A well-proportioned cut will enhance the sparkle and life of the gemstone.

A coloured gem might be cut with sparkling facets, into a smooth domed cabochon, or into a sleek inlay or tablet style. Choosing which you love best, and even combining different cuts, is part of the fun!

It’s no surprise to know natural coloured stones display a wide variety of inclusions and blemishes. After all, they came from the earth.

Clarity is a grade of how visible these inclusions and blemishes are to the naked eye. In general terms, the more inclusions a stone has, the lower its clarity. However as we’ll discover later, multiple inclusions doesn’t necessarily mean an unattractive stone.

Finally, the most important measure of value for a coloured gem – colour.

The colour is, of course, what makes a gemstone so special and valuable. Most sought after are bright and vibrant shades, with consistent colour across the whole stone. Saturation needs to be just right - too pale and the colour isn’t strong enough to the eye, too dark and the stone may not sparkle as much.

What makes a beautiful stone?

There’s a classic saying that a coloured stone’s value is determined by its beauty, rarity and durability – the three traits of gems. Across each trait there are a range of possibilities, so each coloured stone is a unique blend of individual traits and qualities.

Beauty can be subjective - but colour, cut and clarity offer a guide. A beautifully cut stone in a strong vivid colour will always be a stunning choice.

Rarity can be truly exciting when it comes to coloured stones. Coloured gems can be even rarer than diamonds, particularly if they are in unusual or vibrant colours.

Durability is a combination of hardness, toughness, and stability. A coloured gemstone is not much use for jewellery if it is too soft or brittle to be worn without damage. For this reason, you will only find gemstones of a suitable toughness in jewellery.

Most coloured gemstones are durable enough to been worn every day and forever, but there are a small number of delicate stones, such as emerald and malachite, which do require a little extra care.

A good jeweller will always take this into account, setting these stones in earrings and neckwear or protecting them with rubover and flush settings.

But what really matters?

After all, when choosing a coloured stone, the most important decider of beauty is the eye of the beholder.

Whether you’re choosing for yourself or a loved one, don’t consider only how rare or valuable a stone might be, but how it makes you feel. Which colours or cuts draw your eye?

Many people find inclusions incredibly beautiful, and will choose a cut that shows off the individual variations that make a stone unique.

Colour preference is also so personal. Let’s take a blue sapphire – one might love a classic royal blue, while others lust after a pale cornflower shade or a deep, dark navy.

Are you ready to discover your perfect stone?