Carat is the unit of weight for the diamond.  A carat is furthur subdivided into 100 points (0.01 carat = 1 point).  Value per carat increases with carat size, because larger rough diamonds occur less frequently in nature.  In other words, 2 half-carat diamonds purchased together will not cost as much as 1 one-carat diamond, as the one-carat stone is more rare.

Carat weight has no bearing on a diamond's cut, color, or clarity.

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