Our deep dive into gemstones starts with emeralds. You’ve probably heard of emeralds numerous times, yet it’s a wonder this stone is actually made deep inside the earth, naturally, and millions of years ago.
Emeralds stem from two places, either Egypt, where the emeralds are commonly pale green, and highly included, or Colombia, where we often find the most beautiful emeralds. In Colombia, there are two important emerald mines you should know; Chivor and Muzo. Chivor. Chivor originates all the way back to before 1555 and Muzo, a source of larger and even finer crystals, traces back to 1560. Both mines were discovered – or rather stolen – by the Spanish conquistadors from their Native American owners.
The biggest difference between emeralds found at Muzo and Chivor is in what is called the secondary hue, the colour which is not green. The emeralds from the Chivor mine, which is an older deposit, tend to have a slightly bluish secondary hue, while those from Muzo tend slightly toward the yellow.
In 1997 another mine was discovered very close to the Muzo mine, which is called La Pita. The emeralds from La Pita are almost impossible to separate from Muzo stones, however, La Pita, which is a complex of six mines, are responsible for between 60-70 percent of the current production of emeralds in Columbia.
Since the discovery of La Pita, emeralds have been found across the entire world, from Pakistan, Afghanistan, Russia, Bahia, Goias, and even in North Carolina. But the finest will always be the emeralds from Muzo.
So, what exactly do we consider when we are looking at emeralds?
Often, we assess:
- Saturation and Tone
- Clarity and Crystal
- Take care, there are lots of synthetic emeralds on the market.
- The rarity factor
Emerald is one of the primary colour gemstones, which means that the most desirable colour is the purest green possible. Although it is true that a small percentage (10-15%) of yellow colour will enhance the dominant green hue, the purer the green, the finer the stone.
Emeralds personify the pure idea of green. If you close your eyes and picture the richest, purist green you can imagine – that is the colour of emerald.
Emeralds are usually either a bit yellowish or bluish, sometimes we even see both secondary hues in the stone, and the blue can sometimes add richness and warmth to the appearance of the stone.
When you examine an emerald, in all light sources, you should see that incandescent light will bring out the blue. This is the reason why some connoisseurs prefer an emerald which is slightly yellowish in daylight. They feel that a bit of yellow will balance the tendency toward blue under a light bulb. But be aware, if an emerald shows more than 15% blue in incandescent light it is what we call over-blue, and the price drops.
SATURATION AND TONE
To understand saturation and tone, it is easiest if you imagine a glass filled with clear water. Slowly, a green colour is dropped into the water, and the water will progressively turn greener and greener. The colour green is the tone of the stone. As a result, we must assess how green the emerald is. Is it blueish-green? Yellowish-green? Specifically, the saturation is how much of the green colour the emerald demonstrates. Is it a lot of green colour, or is only a faint green?
For emeralds, we will of course look for the greenest of green; the perfect green. Sometimes, we will see emeralds with a greyish overtone, and these I suggest you stay away from, as the grey will make the stone look dull and cool in colour.
CLARITY AND CRYSTAL.
Most often, emeralds are found with some visible inclusions. It is very rare to have an eye-clean emerald above 1 carat and because of this, inclusions are often accepted in emeralds. It is more important to look at the crystal than to try to find a flawless stone. The finest emeralds show a wonderful clear crystal which gives the stone a marvellous inner glow. If the stone shows that, a few visible inclusions – what experts call “jardin” (garden) – are easily forgiven. These stones are exactly what we are looking for.
Most emeralds are cut in what is called the emerald cut. This cut has 17 long, narrow step-like facets and most emeralds are cut in this shape both because it enhances the warm satiny hue of the green, but also because it is the most efficient use of the rough material.
Beware – an overwhelming majority of emeralds available on the market are treated with a variety of substances to enhance the clarity and sometimes the colour of the tone. The rough diamond is often highly fractured, and since earlier times, various oils have been used to hide cracks to improve the clarity of the gem. This practice has been going on for so long, that it has become accepted and is rarely disclosed to the buyer.
Lately, polymer plastics have begun to replace the traditional oiling. Opticon is the brand name of a popular polymer with the same refractive index as emerald and is almost impossible to detect. Surprisingly, there can even be introduced green dye into the polymer filler, which can improve the apparent colour to the stone.
The use of unhardened polymer is acceptable, but dyeing is not.
Many labs have adopted a uniform seven-step classification to describe the treatments of emeralds with colourless or polymers. The classifications are as follows:
- Faint to moderate
- Moderate to strong
- Strong to prominent
Stones which are in the first four classifications are the rarest and worthy of consideration whilst you should avoid stones which fall into the last two classifications.
There are many synthetic emeralds and the best defence against both a treated and synthetic emerald is a certificate from a recognized independent gemmological laboratory.
THE RARITY FACTOR
As with all rare gemstones, fine emeralds are rare in any size. Prices tend to increase at one, five, eight and ten carats and level off at twenty carats.