While sparkle matters, learning about the 4Cs helps you recognise quality when purchasing diamond jewellery.

At OM Jewellers in Perth, we ethically source our diamonds globally from reputed suppliers. A diamond is visually stunning, and a form of investment. Certain elements combine to make a diamond both beautiful and valuable.

Diamonds are graded around the world using the International Grading System, established in the 1940s by the Gemological Institute of America, known as the GIA. This system provides a trustworthy framework.

Having a basic understanding of the language around diamonds will help you select the best possible diamond jewellery for your budget. Here is an explanation of what is commonly referred to as “The 4Cs”.


Your diamond is weighed in metric carats, where 1 carat equals 0.2grams. It is possible for diamonds of the same weight to have different values, because Clarity, Colour, and Cut impact a diamond’s worth.


The inclusions and blemishes present in a diamond impact clarity. Inclusion describes imperfect aspects within the diamond, and blemishes imperfections on the surface — yet even with these elements, diamonds are still very valuable.

A 10x magnification is used, as a diamond may have inclusions not visible to the naked eye. The GIA Clarity scale includes eleven possible diamond clarity grades, with the first two grades the rarest.

FL is a grade used for flawless diamonds, and IF refers to internally flawless diamonds whose inclusions are very difficult to view. The following grades are VVS1 (Very Very Slight Inclusions), VVS2, VS1, VS2, SI1, SI2, and then I1, I2 and I3.


The GIA colour grading scale ranges from D to Z. Colour-wise, the most valuable diamond in this scale, is without colour. The more yellow and brown is detected, the further down the alphabet the diamond is graded.

The GIA colour scale includes:

  • Colourless: D, E, F
  • Near Colourless: G, H, I, J
  • Faint: K, L, M
  • Very Light: N, O, P, Q, R
  • Light: S, T, U, V, W, X, Y, Z

Please note this scale does not cover rarer coloured diamonds. In contrast, the brighter a coloured diamond, the higher its value. Speak to an OM Jewellers specialist if interested in jewellery featuring brown, yellow, pink, or blue diamonds. Learn more about coloured diamonds.


Aside from the many available shapes, the cut of diamond matters because it allows light to interact. The GIA range was created specifically for the popular round brilliant diamonds, and spans Excellent, Very Good, Good, Fair, and Poor.

A mix of factors are evaluated, including Face-Up Appearance, Design, and Craftsmanship.

  1. A diamond’s sparkle combines brightness, fire, and scintillation. These categories measure how light scatters and reflect internally and externally.
  2. Design impacts shape, and therefore weight ratio, proportion, and durability. An OM Jewellers specialist can explain these details to you.
  3. Polish refers to the surfaces of the facets, while symmetry references the way facets are arranged, reducing sparkle if poorly placed.

OM Jewellers and Diamonds

The diamonds we select range from SI to VVS, colourless/diamonds (D-H).  And yes, while our diamonds are from 0.40ct to 2ct, OM Jewellers will source larger diamonds per client request.

Our wide array of high-quality diamond pendants and diamond rings in Perth is why so many view us as the best jewellers in Perth. Visit instore or contact our friendly team to discuss your next diamond purchase.