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What to look for - The Five C's

In a similar way to buying diamonds, the Tanzanite Foundation grades Tanzanite according to the FIVE C's; Colour, Clarity, Cut and Carat Weight. The higher the combination of these characteristics, the rarer and more valuable the tanzanite stone. Understand and check all 5 C's before buying your tanzanite.


COLOUR - Intensity of colour and saturation of blue to violet

Colour refers to colour quality and its degree of saturation. The depth of colour ranges from Exceptional to Pale, with a 'B' or 'V' indicating a predominance of blue or violet hues. The deeper the colour, the rarer the tanzanite. Larger stones are frequently darker and it unusual to find an intensely saturated stone under 5 carat’s in weight.

CLARITY - Description of natural inclusions

Clarity refers to any natural flaws and inclusions in a tanzanite. Tanzanite's ranges from Eye Clean to Heavily Included. The more flawless the tanzanite, the more valuable it is.

CUT - Proportions and brilliance

Cut refers to a tanzanite's brilliance, proportions and finish. An 'Excellent' cut ensures that the stone's facets reflect light to create maximum brilliance. The more precise the craftsman's cutting, the more valuable the tanzanite.

CARAT - A weight measurement, equivalent to 1/5th of a gram

Carat Weight is the term used to measure a tanzanite's weight. One carat has 100 points and weighs 1/5 of a gram. Two seemingly identical tanzanite's will have different Carat Weights if they vary in depth.


The 5th C is Confidence and is only applicable to tanzanite which is accompanied by the Mark of Rarity Tm Tag. The Mark of Rarity Tm is the icon of the Tanzanite Foundation and is synonymous with Confidence. It is assurance that your tanzanite is authentic and has followed an ethical route to market.