GIA’s 4Cs Q&A series continues with a careful consideration of carat weight.

gia carat weightQ: What is the difference between carat and karat?

A: Karat (abbreviated “K” or “Kt”) is a unit of measure that describes the purity–or fineness–of gold.

Q: How did the carat system start?

A: The modern carat system started with the carob seed. Early gem traders used the small, uniform seeds as counterweights in their balance scales. The carat is the same gram weight in every corner of the world.

Q: What are “magic sizes”?

A: Some weights are considered “magic sizes”–half carat, three-quarter carat, and carat. Visually, there’s little difference between a 0.99 carat diamond and one that weighs a full carat. But the price differences between the two can be significant.

Q: How is diamond carat weight measured?

A: To determine carat weight, the grader weighs the diamond using an extremely accurate electronic micro-balance that captures the weight to the precise fifth decimal place (the nearest ten-thousandth of a carat).

To see if your knowledge of carat weight measures up, please check out 4Cs of Diamond Quality or download the GIA 4Cs app, now available on iPhone, iPad, and Android!

Color Q&A | Clarity Q&A | Cut Q&A | Carat Weight Q&A

All diamond images and diagrams are for reference only and may not reflect true diamond carat weight.