Carat (Ct) is the unit of mass (weight) of gemstones, and 1 carat is equal to 0.2g or 200mg ... One carat is divided into 100 minute, such as 50 minutes or 0.5 carat, which is used to calculate smaller gemstones. Because the density of gems is basically the same, the heavier the gem, the bigger the volume. The bigger the gem, the rarer it is, and the higher the value per carat. According to the textual research of Huaxuan Jushi, the unit name of Kela originated from Ghana, a West African country in the13rd century, and its capital Accra is the earliest gold and diamond distribution center in the world. Due to the language communication barriers between countries, trade place names are used as units of measurement.

Carat (ct), usually abbreviated as Ct, has been used as an internationally recognized unit of measurement for gemstones since 1907. CT is the quality unit of jade, diamond and other precious stones, and it is the purity ratio of precious metals. International standard 4C for evaluating diamonds. 4C refers to color, clarity, weight and cut.

The word "Kela" comes from the Greek word "Kela", which refers to carobseed, a plant widely spread from East Asia to the Middle East. Because its fruit is said to have almost the same weight, and the weight of diamond is the most easily measured feature in 4c, the early carob tree was used as the weight unit of jewelry and precious metals. One carat is equivalent to the weight of a small horn tree seed.

From 65438 to 0983, Mr. Tao of Chengdu Institute of Geology (now Chengdu University of Technology) conducted a specific study, which confirmed that Kela originated from the seed of carob in the Mediterranean region-rice bean, and the weight of this tree was about 200 mg, which had nothing to do with the weight of Robinia pseudoacacia, Pittosporum and Sophora japonica as some people said. It was not until the early 20th century that carat weight was standardized.