Sapphires are one of the world's most expensive gems with prices equivalent to similarly weighted emeralds or rubies. They are precious stones of an intense rich blue colour. The weight of a gemstone is measured in carats so they can be compared against other stones for value. You can find the carat measurement of a sapphire by converting the metric reading using a formula.
Place the sapphire on its own on a sensitive metric scale.
Note the weight in grams of the sapphire to the last decimal place.
Convert the grams to carats using the formula: 1 carat = 0.2 grams. Multiply the weight of the stone in grams to get the carat weight of the sapphire. So a stone that weighs 1 gram is the equivalent of 5 carats.