At Simon Lewis Jewellers, every diamond we use is certified by the Gemological Institute of America (GIA) – the world’s most trusted independent gemological laboratory. This means each stone comes with an authoritative grading report covering cut, colour, clarity and carat weight, giving you complete confidence in your purchase.
We source our diamonds and precious gemstones from reputable suppliers worldwide, selecting each stone by hand for its quality, brilliance and character. Visit our Hatton Garden workshop to view our collection and receive expert guidance from our team.
Cut determines how well a diamond reflects light. A well-cut stone will display maximum brilliance and fire, regardless of its carat weight. Cut is the single most important factor in a diamond’s visual appearance, and it is the area where our expertise matters most – we can show you the difference a superior cut makes in person.
Colour is graded on a scale from D (colourless) to Z (light yellow). For most jewellery settings, diamonds in the D to H range appear white to the eye. We help you choose the right colour grade for your specific design and metal choice.
Clarity refers to the presence of internal inclusions or surface blemishes. Most inclusions are invisible to the naked eye, and a skilled jeweller can advise which clarity grades offer the best value without compromising appearance.
Carat weight measures the diamond’s size. Larger diamonds are rarer and therefore more valuable, but the interplay between all four Cs determines a diamond’s overall beauty and worth.
Ruby is one of the most durable of all gemstones, prized for its deep red colour and exceptional hardness. As a variety of the mineral corundum, ruby ranks 9 on the Mohs hardness scale, making it ideal for everyday jewellery including engagement rings and eternity rings. We source rubies from across the world and can help you select the perfect stone for your bespoke design.
Sapphire, like ruby, is a variety of corundum and shares its outstanding durability. While blue is the most recognised colour, sapphires occur in a full spectrum including pink, yellow, orange and padparadscha. Their versatility makes them a stunning choice for engagement rings, pendants and statement pieces.
Emerald is a variety of the mineral beryl, valued for its rich green colour. Most emeralds are mined in Brazil, Colombia and Zambia, with each origin producing distinctive colour variations. Emeralds are softer than diamonds, rubies and sapphires, so they require careful setting and handling. Our craftsmen have extensive experience in working with emeralds and will advise on the best setting to protect your stone while displaying its beauty.
A GIA certificate is an independent, unbiased assessment of a diamond’s quality. Unlike in-house grading, GIA has no financial interest in the sale, which means the grades on the report are trustworthy and consistent worldwide. When you buy a GIA certified diamond from Simon Lewis, you know exactly what you are getting – no guesswork, no inflated grades, just an honest assessment from the world’s leading gemological authority.
A GIA certified diamond has been independently assessed and graded by the Gemological Institute of America. The GIA report details the diamond’s cut, colour, clarity and carat weight, along with other characteristics. This certification provides an objective, trusted evaluation that is recognised worldwide.
The round brilliant cut is the most popular choice for engagement rings due to its exceptional brilliance and versatility. However, the best shape depends on personal preference and ring design. Oval and cushion cuts offer a vintage feel, while emerald cuts provide a distinctive geometric look. Visit our workshop and we will show you each shape in person to help you decide.
Yes. If you have a diamond or gemstone you would like us to set into a new design, we are happy to work with your stone. We will assess its condition, discuss suitable settings and create a bespoke piece around it. This is a popular option for clients redesigning inherited or heirloom jewellery.