K colour is a diamond colour grade in the GIA Diamond Grading System, sitting at the upper end of the Faint range and immediately below the Near Colourless J grade. K-colour stones show a perceptible warm body colour when viewed face up against a white background and a clearly visible yellow or brown tint when viewed table-down against a grading tray.

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Position in the GIA scale

The GIA scale runs from D, the highest colourless grade, through Z, the lowest grade before fancy yellow. The scale is grouped into ranges: D-E-F Colourless, G-H-I-J Near Colourless, K-L-M Faint, N to R Very Light, and S to Z Light. K is the first grade in the Faint range and the first grade at which most experienced graders can detect body colour reliably under face-up conditions on a half-carat or larger stone, although K stones in smaller sizes can still appear effectively white in many mountings.

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Appearance and mounting choice

The face-up appearance of a K-colour diamond depends strongly on the mounting metal. In yellow gold the warm body colour blends with the metal and is much less visible. In white gold or platinum the warm tint is more apparent against the white background. Many experienced jewellers therefore recommend yellow gold or rose gold mountings for K-colour centre stones, particularly in larger sizes, where the metal disguises the body colour and the consumer benefits from the substantial price discount relative to higher grades.

Trade context

K-colour stones trade at a meaningful discount to G-H-I near-colourless grades and offer a favourable size-to-price ratio for buyers willing to accept the warm tint. The discount per grade through the K-L-M range is among the steepest on the colour scale, reflecting the visible difference at this point and the consumer preference for stones described as colourless or near-colourless on grading reports. K colour is therefore a common choice for value-oriented engagement and statement rings, particularly where carat weight is a higher priority than absolute colour purity.