The Gemstone Guide

Including sapphire, emerald, ruby, tanzanite and aquamarine - inorganic crystalline materials formed through geological processes.

Such as pearl, which originate from living organisms rather than mineral processes.

Such as lapis lazuli, which are made up of multiple minerals rather than a single mineral crystal.

You may also hear gemstones described as "precious" or "semi-precious."

Traditionally, diamond, ruby, sapphire and emerald were grouped as precious stones, while most others were described as semi-precious.

Today, that distinction is increasingly outdated and isn't a reliable indication of quality or value. An exceptional gemstone outside the traditional "precious" group can be considerably rarer and more valuable than a lower-quality ruby, sapphire or emerald.

What matters is the individual stone.

Emerald is the green variety of beryl and is prized primarily for the quality and intensity of its colour.

Natural inclusions are common and often accepted as part of an emerald's character, so clarity expectations are very different from those applied to diamonds.

At 7.5–8 on the Mohs scale, emerald has good scratch resistance but generally requires more care than sapphire or ruby, particularly for jewellery worn every day.

Sapphire is a variety of corundum and ranks 9 on the Mohs scale, making it one of the more durable coloured gemstones for everyday jewellery.

Although best known for blue, sapphire occurs naturally in a wide range of colours including pink, yellow, green, orange and purple.

Colour is generally the most important consideration, with hue, tone and saturation all influencing appearance and value.

Ruby is the red variety of corundum, meaning it belongs to the same mineral family as sapphire.

Its colour can range from lighter red through to deep, vivid red, with colour typically having the greatest influence on beauty and value.

Like sapphire, ruby ranks 9 on the Mohs scale and is one of the stronger coloured gemstone choices for regular wear.

Tanzanite is the blue-to-violet variety of zoisite and is known for its distinctive colour and pleochroism, meaning different colours can be visible when viewed from different directions.

At around 6–7 on the Mohs scale, it requires more care than sapphire or ruby.

Aquamarine is the blue to slightly greenish-blue variety of beryl - the same mineral family as emerald.

It's known for its clear, watery colour and typically high transparency, with stronger blues generally attracting more interest than very pale stones.

At 7.5–8 on the Mohs scale, aquamarine can work beautifully in rings as well as earrings and necklaces. It's also the traditional March birthstone.

Our take: A great option if you love blue gemstones but want something softer and more understated than traditional blue sapphire.

Amethyst is the purple variety of quartz, ranging from delicate lilac through to deep, saturated violet.

With a Mohs hardness of 7, it's suitable for many types of jewellery, although we'd be more cautious with an engagement ring intended for constant wear.

It's the traditional February birthstone

Our take: Amethyst provides a huge amount of colour and character without the price associated with rarer coloured gemstones.

Alexandrite is particularly unusual because of its ability to change colour under different lighting.

Fine examples can appear greenish in daylight and shift towards red or purplish-red under warmer incandescent light.

It's a variety of chrysoberyl and ranks 8.5 on the Mohs scale. Natural alexandrite with a strong colour change is also genuinely rare, particularly in larger sizes.

Our take: If you want something genuinely unusual rather than simply a different gemstone colour, alexandrite is one of the most interesting stones we can source.

Citrine is the yellow-to-orange variety of quartz, ranging from pale lemon through to warm golden and reddish-orange tones.

Much of the citrine available commercially is produced by heat-treating amethyst, so treatment disclosure is worth understanding.

At 7 on the Mohs scale, it requires more care than sapphire, ruby or diamond.

Our take: Citrine works particularly well when you want warmth and colour without moving into the pricing of rarer yellow gemstones.

Garnet isn't one gemstone but a group of closely related minerals.

Although deep red is the colour most people associate with garnet, different varieties can produce orange, pink, purple and even vivid green stones.

One of the most desirable green varieties is tsavorite garnet.

Our take: Don't dismiss garnet based on the traditional red version alone. The family has considerably more variety than most people realise.

Morganite is the pink-to-peach variety of beryl, placing it in the same mineral family as emerald and aquamarine.

Its soft blush tones work particularly naturally with rose gold, although white and yellow metals create very different finished looks.

With a Mohs hardness of 7.5–8, it has reasonable scratch resistance.

Our take: Worth considering if you want a soft, romantic colour rather than the stronger saturation of a pink sapphire.

Moonstone is best known for adularescence - the soft, floating glow that appears to move across the stone as it catches the light.

It's considerably softer than sapphire or ruby, so we'd generally favour it for earrings, pendants and carefully worn pieces rather than an engagement ring intended for unrestricted daily wear.

Our take: Moonstone is less about brilliance and more about the unusual way it interacts with light.

Peridot is the gem variety of olivine, with colours ranging from yellowish-green through to richer green.

At approximately 6.5–7 on the Mohs scale, it requires a little more care than harder gemstones. It's also the traditional August birthstone.

Our take: Peridot has a distinctive fresh green that looks completely different from emerald. It's well worth comparing the two side by side.

Spinel occurs naturally in colours including red, pink, purple, blue and violet.

Red spinel was historically mistaken for ruby, and fine red, pink and cobalt-blue examples can be particularly desirable.

With a Mohs hardness of around 8, spinel also offers good durability for fine jewellery.

Our take: One of the most underrated gemstones - strong colour, good durability and something less expected than ruby or sapphire.

Topaz occurs in several colours including colourless, blue, yellow, orange, pink and reddish tones.

It ranks 8 on the Mohs scale, but hardness doesn't tell the whole story: its crystal structure means it can cleave if struck in the wrong direction.

Our take: Topaz offers far more than the familiar blue varieties. We'd start with the colour you want and then explain how treatment, rarity and value differ.

Tourmaline has one of the widest colour ranges of any gemstone family, appearing in pink, red, green, blue, violet and combinations of multiple colours within a single stone.

Varieties include red-to-pink rubellite and intensely coloured blue-to-green Paraíba tourmaline.

Our take: One of the best places to look if you know the colour you want but aren't fixed on a particular gemstone.

Zircon is a natural gemstone in its own right and shouldn't be confused with cubic zirconia, which is a laboratory-made diamond simulant.

Natural zircon occurs in several colours and can show impressive brilliance and fire.

Although reasonably hard, it can be more vulnerable to abrasion and chipping than its hardness alone might suggest.

Our take: Natural zircon is a genuine and fascinating gemstone, particularly if you're looking for strong brilliance in something less commonly seen.