1 carat = 200mg = 0.2g.
Diamonds weighing less than 1 carat are usually measured in "points", 1 carat = 100 carat. On the certificate of diamond, the weight of diamond is accurate to the third decimal place.
Since 1907, carat (Ct) has been used as an internationally recognized gem measurement unit, which is the quality unit of pearls, diamonds and other gems and the purity ratio of precious metals. International standard 4C for evaluating diamonds. 4C refers to color, clarity, weight and cut.
IGI uses an electronic balance with an accuracy of 0.0000 1 carat to weigh the accurate weight of diamonds, and records it in the diamond appraisal report, accurate to two decimal places. So a 25 cent diamond weighs 0.25 carat. Diamonds of the same quality, the greater the weight, the more precious.
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.
Extended data:
The origin and history of carat
1. According to the textual research of Huaxuan layman, 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.
2. The word carat comes from the Greek word carat, which refers to carob, 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.
3.65438-0983 According to the specific research of Mr. Tao from Chengdu Institute of Geology, it is confirmed that carat as a weight unit comes from Mi Dou, the seed of carob in the Mediterranean region. The weight of this tree species is about 200mg, which has nothing to do with the weight of Robinia pseudoacacia, Brucea javanica and Sophora japonica. It was not until the early 20th century that carat weight was standardized.
Baidu encyclopedia-Kela