💎 What a Gem! 💎

The Five C’s of Gemstones and what they mean!

Gemstones and gemstone jewellery are popular gifts, often symbolising love and appreciation.

Whether it be for Mother’s Day, a birthday, anniversary or an engagement, the impact the five C’s have on the quality of the gemstone and therefore, how valuable it is.

Understanding cut, colour, clarity and carat will allow you to gain a better understanding of the true value of the stone before deciding how much to bid.


The cut of a gemstone is the only property which is totally out of the hands of nature. Cut refers not only to the shape and style of the gemstone, but its proportions, symmetry, and finish or make.

The proportions and angles of the gemstone determine how much light enters and exits and the direction the light travels. This affects the brightness and sparkle of the gemstone and therefore how attractive you find it!

The most popular diamond cuts include round, pear, emerald and princess. Gemstone cutters work for years to master their trade and try to make the best use of natural light. This can directly impact the overall value of your jewellery. 


All gems have a preferred colour or a small range of preferred colours. The more the colour varies from this range, the less valuable the gemstone.

When it comes to coloured gemstones, the colour quality takes precedence.

Gemstone colour can be broken down into three categories: hue, tone, and saturation.

Hue refers to the specific colour of the stone, for example, blue or purple. It is most preferable for a stone to have the purest hue possible. This means that any other colour should either be non-existent or minimal.

Tone describes the level at which the colour is seen in the stone. A gemstone can be green, but it can be a very light, pastel shade of green, display a dark green colour or be extremely bright green.

Lastly, the saturation of a gemstone is how intense its colour is and if there are any grey or brown hues present.

Most gem quality diamonds fall within a range from “D” colourless, to “Z” light yellow. Although almost all diamonds will have a trace of yellow, brown or grey body colour.

Except for some natural fancy colours, such as blue, pink, purple, yellow or red, the colourless grade diamond is the most valuable.


Gemstones may have various inclusions or imperfections that are a result of the natural formation of the stone. The number and size of these influences how the stone reacts to light and therefore, decides the clarity grading.

Most imperfections in gemstones are not visible to the naked eye. For this reason, clarity is determined under 10x magnification.

Clarity is measured on a scale that ranges from flawless to stones that have visible imperfections. 

Each variety of gemstone has its own clarity standards. For example, Tanzanite tends to be a virtually inclusion-free stone, while Emeralds almost always features some sort of inclusion.

A flawless diamond is one that has no inclusions or flaws and allows light to pass through without interference. These are much rarer and as a result much more expensive. 


The size of a gemstone is measured, not by its dimensions, but by its weight. The weight of a gemstone is expressed in carats. 1 carat is equal to 0.2 grams. 

Weight is the most obvious factor in determining the value of a gemstone. People would generally assume that the bigger the better, and therefore more expensive. However, with gemstones, it is not so black and white.

For example, there are some gemstones such as the ruby, which are often found in large sizes. Sometimes they are so big, they are not practical or usable for jewellery. This makes them less valuable. However, it is extremely difficult to come across a ruby with high clarity.

Two gemstones of equal weight can have very unequal values, depending on their quality. It is also important to realise that jewellery featuring one gemstone weighing 1 carat is usually worth more than jewellery containing two 0.50 carats gemstones.  


While gemstones and jewellery can be the ultimate symbol of love, they also represent an investment in time, energy and money.

The final member of the 5 C’s is the gemstone certificate and it has an increasingly important role in measuring the quality and value of a stone.

A gemstone certificate should include a plotted diagram of the stone and all significant characteristics, including cut, colour, clarity, and carat weight.

It should also comment on the characteristics like fluorescence, graining, and any notable characteristics of the gemstone. A good laboratory will also determine whether the gemstone has been treated. Treatments to enhance the colour and purity can significantly reduce the value.

Most often the certificate will estimate the replacement value of the stone for insurance purposes. 

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Matt Kalinski

Head Of Valuations

Qualifications & Affiliations

American Society of Appraisers Candidate Member

Certified Practicing Valuer AVAA


Matt has been in the valuations space for many years and has extensive experience in the space across an abundance of various industries. He now leads the valuations teams for Lloyds Auctions with a passion for encouraging his team to set and achieve high goals and produce great results for the company whilst growing the team’s skills starting with a great culture and team mindset.