Gemstones 2017-05-19T10:12:19+00:00

Gemstones

To help you with choosing the right gemstone, we’ve put together a table that shows suitable ring stones by colour. You’ll see that we’ve divided each colour into dark and light. A ‘dark’ stone will have a strong, rich colour — difficult to see through. Most of the dark stones do have lighter versions – however, many of the light stones are generally only light. A ‘light’ stone is much easier to see through. At the extreme, some light stones will look almost colourless or show just a hint of colour.

In the following list, we’ve only included stones that we recommend as suitable for setting in a ring. There are many others, but because they’re relatively soft (easily damaged) or of low value, we haven’t included them. You may particularly note that some popular stones such as iolite and peridot have been omitted for these reasons. We have also included a few additional notes to help with choices.

Of course, if you really don’t have much of a clue, take a look at the section on birthstones— or check out the jewellery your partner’s already wearing. This might give you some ideas as to what you should go for.

Colour Range Gemstones
Black-grey Diamond, spinel, sapphire (grey is actually not that easy to find – more of a muddy light purple)
Blue Dark Diamond, sapphire, spinel, tanzanite
Light Aquamarine, zircon, topaz (beware, the super bright ones are usually irradiated)
Green Dark Emerald, sapphire, tsavorite garnet, tourmaline
Light Sapphire, green beryl
Yellow Light Diamond, sapphire, citrine, golden beryl, topaz
Pink Dark to medium Diamond, sapphire, spinel, malaia garnet, topaz, tourmaline
Orange Dark to light Hessonite garnet, citrine, sapphire (bright orange often treated with beryllium)
Red Dark to medium Ruby, garnet, topaz, tourmaline, spinel
Purple Dark to light Sapphire, amethyst, garnet, spinel

Gemstone 101 – what you need to know

When it comes to gemstones, not only is there a lot to choose from, but there are also lots of traps for the unwary. Imitation, synthetic (often incorrectly described as ‘created’) and treated stones are common, so it’s possible to get ripped off if you’re not dealing with a reputable trader. If you want to be sure you’re getting what you paid for, insist on having the stone or stones tested at an independent gem laboratory before you buy (generally they won’t value a stone for you, but they will tell you whether it’s real or not).

The four gemstone ‘C’s + ‘H’

Like diamonds, when choosing a gemstone, you need to consider cut, carats (size), clarity and, most importantly, colour. Also, like diamonds, the value of a particular gemstone depends on its rarity, size and quality. And when it comes to rarity, often it’s a colour that can be rare within a particular type of gemstone (take pink diamonds as an example — still a diamond, but much more expensive than white diamonds). This is where the deception can come in. Often it’s possible to alter the colour of a gemstone through chemical, heat or radiation treatment, making it a more valuable colour (or in an attempt to pass the stone off as a different type of gem all together).

We also think it’s important (when buying stones for a ring that will be worn all the time) to consider ‘H’ — hardness. Many gemstones are relatively ‘soft’ or fragile and will get damaged easily if worn on the hands rather than, say, in a pendant.

Colour

In gemstones, colour is described in terms of:

  • Hue — its pure spectral colour (from red to violet)
  • Intensity — the brightness or dullness of the colour
  • Tone — the amount of background white, black, grey or brown
  • Distribution — the evenness (or unevenness) of colour

The actual colour of a stone is a combination of its pure spectral hue and background white, black, brown or grey tint. The pure spectral and background colours go together to create the tone. For example, if white is present with red, the stone will appear lighter in colour. If black is present, the stone will appear darker. Generally, the closer a stone is to the pure hue, the more valuable it is considered.

By the way, the light source you use is very important when evaluating a stone. Different types of artificial lights emit different spectra and can have a significant impact on the appearance of a stone’s colour. Fluorescent lights are typically weak in red rays (they’re ‘cool’) and, as a result, red stones like rubies and garnets appear to be a darker purple-red compared to when they’re viewed under incandescent or daylight (both of which are strong in red rays).

Blue stones (like sapphires), on the other hand, are best viewed under fluorescent light or in daylight. Under incandescent light they appear much darker — almost black. Be aware too that background colour impacts on how a stone appears. Red stones appear even redder when viewed on an orange or yellow background. Diamonds are often displayed on a blue background to reduce any yellow tones.

Clarity

When it comes to gemstones, flaws are generally more prevalent than in diamonds, and you’ll often encounter cracks (also called ‘feathers’) as well as physical inclusions. The positioning of cracks can be very important — both from an aesthetic point of view and in terms of fragility. A crack in the wrong place could cause a stone to break when it’s being set.

As for inclusions, their aesthetic importance varies with the tone of the stone. The darker the stone, the less visible inclusions are. Inclusions are more visible in light, almost transparent stones. Importantly, flawless gemstones are extremely rare and very expensive. If you do encounter a “flawless” gemstone, view it with suspicion. It could easily be an imitation or a synthetic*. The only way to be certain is to have it independently tested by a professional Gemmologist.

Finally, the presence of inclusions can, in some instances, be desirable. Gemmologists often use the type of inclusion to identify the authenticity and origin of a stone. Certain inclusions will confirm a stone’s rarity (or not) depending on its origin as, though two stones may look the same to the untrained eye, one could be much more valuable than the other because of its origin – even though it might have more inclusions.

Contrary to popular belief, a synthetic gem material is not an imitation. Synthetic gemstones refer to gems that have the same physical, optical and chemical properties as their naturally grown counterparts, but are created in a laboratory. Any synthetic gem material that does not have a direct natural counterpart is considered an imitation. There is absolutely nothing wrong with purchasing synthetic material, as long as you know that is what you are buying. Synthetic material must be disclosed by the seller. With the exception of moissanite (a diamond substitute), we do not offer laboratory grown gem material.

Cut

As with diamonds, it is the cut that reveals the true beauty of a gemstone. Cut quality affects the depth of colour and the liveliness of the stone. Poor cutting can cause an otherwise beautiful gemstone to look drab and dull; however, good cutting can’t artificially enhance a low quality stone. If the gemstone you are looking at is below par, examine the cut. If the cut is good, you can assume the stone wasn’t good to start with. If the cut is poor, you could (possibly) be looking at a good stone cut badly. A good quality but poorly cut gemstone can be recut, but gem cutters are not magicians — they can only subtract, so the recut stone will be smaller than the original.

Carat

Between types of gemstones, carat weight cannot be used as indicator of relative size; different gem materials have different densities (specific gravity). Whilst weight is useful in valuation, generally physical dimensions (width, length and depth in millimetres) are more commonly used to describe the size of a gemstone. Note, unlike diamonds, bigger does not necessarily mean more valuable. Some gemstones (for example, aquamarine) are commonly available in sizes over 10 carats. In other precious stones (for example, alexandrite, ruby and tsavorite (a green variety) garnet) stones more than 5 carats are extremely rare.

Hardness

When it comes to rings in particular, because they tend to receive a lot of rough handling, hardness of the set stones is important. The harder a stone, the less likely it is to get scratched or chipped in day-to-day wear. The same can be said for any gemstone that has natural cleavages (fault lines). Material such as topaz and diamond can be broken if you manage to hit the ‘sweet spot’. You have to bear in mind that hardness refers to ‘scratch’ hardness, not necessarily robustness.

Of course, you can set some softer stones if you take appropriate precautions in the ring design. Claw setting an emerald isn’t ideal for example, because emeralds are fairly brittle (due to the presence of natural flaws). Putting them in a bezel (or rub-over) setting will, on the other hand, do a better job of protecting the stone from damage.

Again, this is a matter of personal preference and the risk you are prepared to take. Hardness in stones is measured in terms of Mohs’ scale, which rates stones from one to 10. Talc is softest, diamond is hardest (by the way, Mohs’ scale isn’t linear. The ‘gaps’ get bigger as the hardness increases, particularly between 9 and 10 where diamond is exponentially harder than the next hardest, corundum, sapphire and ruby).

If you want to claw-set a gemstone for every day use, our recommendation is that you do not choose a stone of hardness less than 8.0 on Mohs’ scale. If you go for a bezel or channel setting, you can go down to 7.0, as long as the stone is otherwise quite robust.