The Secret to Sparkle
1. Diamond Cut
The cut of a diamond is the single most important factor in its beauty. It determines how light reflects through the stone and how much brilliance and fire it emits.
Cut doesn’t mean shape (like round, oval, or radiant); it refers to proportions, symmetry, and polish. A perfectly cut diamond reflects light back through the top, creating a bright, lively sparkle. A poorly cut diamond leaks light through the sides or bottom, appearing dull or dark.
Gemological labs such as the GIA and IGI grade cut on a scale from Excellent to Poor, assessing how effectively the diamond returns light. The GIA only grade round diamonds for their cut and no others, be wary of cut grades being awarded to non round diamonds as the retailer might have simply made it up - yes, really!
At London Diamonds, every stone we hand select is evaluated for exceptional cut quality to ensure maximum brilliance — even in low light.
For certain shapes such as oval, pear and marquise cuts we check for ‘bow tie effect’ which is where a poorly cut diamond will have a dark shadow across its centre. It’s impossible to avoid completely but this isn’t noted on the certificate and actually has as much bearing on the appearance of the diamond as its colour and clarity. We pride ourselves on ensuring each diamond we select has not only a high grading but exceptional levels of sparkle and limited bow tie effect as well as the correct dimensions for its weight.
From D to Z
2. Diamond Colour
The colour of a diamond refers to the presence or absence of colour tint within the stone. Diamonds with less colour are considered more desirable and are graded higher on the GIA D–Z scale, with D–F representing the most colourless stones.
Colour typically results from trace elements during formation. Stones with pale yellow or brown tones allow less light to pass through, reducing brilliance. Conversely, a colourless diamond allows light to travel freely, producing more fire and sparkle.
Lab grown diamonds are created in controlled environments where mineral contamination is minimal, resulting in a greater proportion of colourless or near-colourless stones. While mined diamonds vary widely in colour, most lab diamonds fall between D and G, offering exceptional value for amazing clarity and brightness.
We tend to only use diamonds which have been graded as D or E colour and VVS clarity. Where a diamond has a lower grading than this, but the same appearance to the human eye, it will be offered at a lower price point.
Like a Fingerprint
3. Diamond Clarity
Clarity measures how free a diamond is from internal inclusions or external blemishes. These tiny marks form during the diamond’s creation and make each stone one of a kind.
The GIA and IGI clarity scale ranges from Flawless (FL) to Included (I). Higher grades have fewer inclusions visible under 10x magnification, though many lower-graded diamonds appear perfectly clean to the naked eye.
Lab grown diamonds usually form with fewer inclusions than mined stones, offering excellent clarity and eye-clean appearance at a more accessible price.
At London Diamonds, we still hand-inspect every diamond to ensure inclusions are invisible without heavy magnification — creating diamonds that look flawless where it matters most: to the eye. There is no point paying for ‘quality’ that no one can see, after all.
Weight VS Size
4. Diamond Carat
Carat measures a diamond’s weight, not its physical size — though the two are closely related. One carat equals 0.2 grams, and even a small increase can significantly affect a diamond’s price.
It’s a common misconception that carat alone determines a diamond’s beauty. In reality, cut, colour, and clarity play equally important roles. A smaller diamond with perfect proportions can appear more brilliant than a larger diamond with inferior cut quality.
Because lab grown diamonds offer greater value per carat, buyers can often choose a larger stone without compromising on quality or ethics.
At London Diamonds, we help clients find the perfect balance between carat weight, proportions, and budget — ensuring every diamond delivers maximum visual impact.
We tend to ignore carat weight and prefer to focus on dimensions as the priority. A well cut 1.80ct oval can have the same face up appearance as a poorly cut 2.05ct one.
