It is the mass unit of colored gems and diamonds, and also the purity ratio of precious metals. 1907 has been used since it was internationally recognized as a gem measurement unit. In the jewelry industry, the unit of measurement for gems is usually carats. Carat (Ct) is the unit of mass (weight) of precious stones, and now it is determined that 1 carat is equal to 0. 2 grams or 200 milligrams. What is the unit of measurement for precious stones? 1. In the jewelry industry, the unit of measurement for precious stones is usually Jin Kela 2. Answer: carat 3. Carat is a unit of weight and is usually used as a unit of measurement for precious stones. 1 carat is 200 mg. Why are bagged potato chips always full of gas? Is it moisture-proof and shatterproof or does it look more? Please refer to the other two articles for the answer of Ant Manor.