Cut grade is the quality of the final shape of the stone, which includes the overall finish, the proportions, and how well the stone’s facets refract light. This grade is considered to be the most important one in determining a diamond’s beauty, and the grades range from Ideal to Poor.

Clarity grade reveals how clear the diamond is, with regard to internal flaws known as inclusions. Clarity is graded at 10x magnification because many flaws are small, but the most important thing is how the stone appears to your eye and how it looks in a setting. Large visible or black flaws will instantly draw the eye. The clarity scale is as follows: Flawless, Very Very Slightly Included (VVS1 and VVS2), Very Slightly Included (VS1 and VS2), Slightly Included (SI1 and SI2) and Included (I1, I2, and I3).

Colour grade represents the lack of colour, rather than the presence of colour, as the hallmark of quality in a stone. A colourless stone is the highest value, and the lowest letter on the grading scale. D and E graded stones are colourless, and they proceed to become more coloured as they advance down the alphabet. G-J are near colourless, K-M are faint yellow, N-R are very light yellow, and S-Z are light yellow.

Carat weight is the physical weight of the stone measured in units known as carats. A larger, deeper-cut stone may not appear larger than a shallower cut peer for this reason.