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Coloured Gemstone Guide

Coloured gemstones can be an excellent alternative to diamonds as they add vibrancy and character to your jewellery. Many factors will determine the value of a gemstone, so it is essential to be informed before making a purchase.

Jump to:
  • What type of gemstones can I find at 77 Diamonds?
  • What should I look for when purchasing gemstones?
  • Our Promises

What type of gemstones can I find at 77 Diamonds?


A symbol of wisdom, sincerity and trust, sapphires have been a prized and beloved gift among royals. Today, this stunning blue coloured gem is extremely sought-after and represents a stable long-term investment.

Sapphires are almost as hard as diamonds – an ideal option if you intend to wear your jewellery on a daily basis. They are the second most chosen gemstone after diamonds for engagement rings. Princess Diana’s engagement ring, now worn by the Duchess of Cambridge, is well-known for its 12-carat Ceylon sapphire, for example. Sapphires are the birthstones for those born in September.


Considered the “gem of gems”, the ruby is the most prized gemstone of all. Its extreme rarity makes it a jewel of unparalleled value. This is why a large ruby will see its price increase exponentially compared to one with a smaller carat weight.

Due to its intense, fiery red colour, rubies have been a symbol of passion and love for centuries. Like sapphires, rubies are very resistant and can be worn every day. Rubies are the birthstones for those born in July.


Celebrated for their intense green colour and healing properties, emeralds have long been a favourite among many notable figures. It is said Cleopatra was particularly fond of this precious gem as a royal adornment.

Symbolising peace, hope and the prospect of a new start, emeralds are a meaningful gift when elegantly set in a fine piece of jewellery. Emeralds are the birthstones for those born in May.

What should I look for when purchasing gemstones?

Intensity of colour
Intensity of colour should always be your main focus when purchasing gemstones, as it will determine the long-term value of your stone.

The most sought after colour intensity is Vivid because it reaches the optimal balance of colour saturation. The more saturated or intense the colour, the darker your gemstone will appear, significantly lowering its value.

On the other hand, a faint intensity can change the colour of your gem altogether. A very light-coloured ruby, for example, becomes a pink ruby.

Unlike diamonds, there is no internationally accepted colour grading system for gemstones. 77 Diamonds have adopted the ICL’s seven levels of colour intensity:

  • Dark: a moderate to strong saturation with a very dark tone.
  • Deep: a moderate to strong saturation with a medium dark to dark tone.
  • Vivid: a vivid saturation with a medium to medium dark tone. Considered the finest combination of tone and saturation.
  • Intense: a moderate saturation with a medium light tone.
  • Medium Intense: a moderate saturation with a light tone.

Sapphires benefit from two further levels of colour intensity:

  • Light: a slightly greyish or brownish saturation with a light tone.
  • Very Light: a greyish saturation with a very light tone.

The size of a gemstone is mainly determined by carat weight. One carat is equal to 0.2 grams and is often divided through a point system, where 100 points make up a single carat unit. The larger the gemstone, the rarer and more valuable it becomes.

Due to their rarity, the price of certain gemstones increases exponentially with size. For example, a 10.0 carat ruby can be, on average, a hundred times more expensive than a 1.0 carat ruby.

The ICL grading system is very straightforward, as it is based on what can be seen by the unaided eye without using magnification.

Unlike diamonds, inclusions in gemstones are common, well-accepted and often serve to indicate the origin of the stone. There are three levels of clarity:
  • “Eye Clean” (EC1 - EC2) indicates that inclusions are invisible to the unaided eye.
  • “Visible inclusions” (VI1 - VI2) indicates that inclusions are only slightly visible to the unaided eye.
  • “Included” (I1 - I2) indicates that inclusions are obvious to the unaided eye.

The origin of gemstones, unlike that of diamonds, can be easily traced due to the unique aspect of the inclusions found in each stone. You can look at them as gemstone “birthmarks”.

Origin has an important impact on the value of gemstones. Stones from certain locations, such as Kashmir sapphires or Burmese rubies, are extremely valuable due to heritage and scarcity.

Most gemstones are regularly treated to enhance colour or clarity. This is a widely accepted practice in the jewellery trade and most methods have no harmful effect on the stone. Put simply, it is a method to speed up the process nature couldn’t finish.

Only the finest and rarest gemstones are unearthed in a perfect state without need for further treatment, making them significantly more valuable.

The most commonly used enhancements are through heat, these include:
  • Heat treatment (H).
  • Heated treatment with flux (Hf1, Hf2, Hf3).

There are also treatments involving the use of oil or resin to fill certain fissures in the stone and enhance clarity. These types of treatments are usually applied to emeralds and are commonly used in the industry.

At 77 Diamonds, we wish to offer only the most durable gemstones. For this reason, we do not sell items that have been treated through more abrasive methods as this weakens the gem. These procedures include heat treatments using lead glass, cobalt, beryllium or titanium.

The shape of a gemstone will not have an impact on price, as this is largely a matter of personal preference. The most common shapes are Round, Oval, Cushion, and Pear.

Gemstones usually combine two different cuts, the brilliant and the step, for an optimised balance of vivid colour and brilliance. Similar to diamonds, the crown of a gem is usually formed into a brilliant cut to add radiance, while the pavilion is step cut, allowing for intense colour and vibrancy.

We also offer less conventional shapes, arranged in the three following categories:

  • Rectangle (Octagon, Fancy Octagon and Baguette).
  • Square (Square, Princess and Asscher).
  • Other (Kite, Trilliant, Shield and Tapered Baguette).

Emeralds are usually cut into a rectangular shape to ensure greater durability, as they are slightly more brittle than other gemstones.

Colour, clarity, origin, treatment and carat weight are all factors that will determine the final price of a gemstone. Bear in mind that high-quality gems are extremely rare and will benefit from a significant increase in value.

Before purchasing a gemstone, it is best to form an idea of the level of quality you are looking for. Try to decide what is most important to you and see how that correlates with your budget.

Our Promises

Responsible Gemstone Sourcing

The tradition of gemstone mining has existed as long as civilisation itself. Over the centuries, it has evolved into a thriving industry, spanning six continents and 47 countries. The activity supports the livelihoods of many individuals: around 75% to 80% of the world’s gemstones come from artisanal small-scale mining, an activity predominantly conducted by family-owned businesses. While it represents an important source of income for communities, artisanal gemstone mining can sometimes lead to poor work conditions and environmental degradations, as some miners lack the knowledge or technological resources needed to protect themselves and the environment.

How do we improve this? Experts in the industry agree that boycotting all gemstone sales would have a detrimental effect on local communities, who survive thanks to their trade. But improving this industry has become a clear necessity to ensure workers’ wellbeing and prevent any further environmental damage.

One of the main obstacles in improving this trade is the difficulty in tracing a stone’s origin. From mine to market, a gemstone will typically go through a series of handlers and traders, often located on the opposite sides of the world.

A first step in improving the industry is for retailers to clearly map out their supply chain. At 77 Diamonds, we are currently working to better understand our own, so we can make decisions aimed towards sustainability and look for improvements where necessary.

As we embark on this journey, we understand the gemstone industry cannot be changed overnight, and this will require time, patience and dedication. But small steps can bring about big change: by first educating ourselves on the way gemstones are produced, we can better educate others and help find alternatives that are both sustainable and contribute to the welfare of miners.

We are collaborating with our suppliers to promote better practices in the industry, and are currently working to provide our customers with a range of gemstones that can be traced directly back to the mine. Our suppliers are also working with vendors to uphold shared commitments of responsible sourcing, which will sometimes include independent desk-based and, where possible, on-site assessments of mines.

Individual Certification

Unlike diamonds, gemstones do not benefit from an international grading standard. 77 Diamonds are working closely with the International Colored Gemstone Laboratory (ICL) to provide individually-certified gemstones that comply with our exacting standards.

We also provide a range of gemstones from highly regarded gemstone laboratories who have long and credible track records in testing and appraising gems. These include GIA, AGL, Lotus Gemology, Pearl and Gem Lab, GRS, Thai Lab and the London Gemstone Laboratory.

On each certification, you will find the gemstone’s colour and clarity grade (as delivered by the laboratory), as well as carat weight and proof of origin.

High-quality Photographs and Visuals

Purchasing a gemstone demands an important level of research and preparation. To help you make the best possible choice, and to ensure transparency on all our items, we offer high-quality photographs and a 360° view of each individual stone.

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