Your confusion is phonetic. Here are words that all sound the same -- in English -- but carry entirely different meanings, depending on how they are spelled.
Although in some silly situations, one could dangle a diamond in front of someone as a reward, then the diamond would be called a carrot.
Carat is a weight indicator of diamonds. Carrots are vegetables, which don't occur in diamonds.
You purchase carrots at the local farmers market. There are no carrots in diamonds. Gem-quality diamonds, however are weighed in carats: your local jeweler can weigh your diamond and give you its weight in carats.
Carrots are not known for either their diamonds or their mills.
Carrots and diamonds aren't related. However, gemstones are weighed in carats, and this includes diamonds. And the card suit "diamonds" is "carreaux" in French. That's sort of close.
Diamonds made in factories are called man-made diamonds.
You can find carrots in the garden. Diamonds are weighed in carats, sometimes called points when the carat weight is less than one carat. The numbers are the same. For example, a diamond that weighs .86 carats contains 86 points.
Essentially, diamonds are rocks. They are also called ice.
Loose diamonds are called loose diamonds. When set as a group, the term may describe the setting more than the stones, i.e., pave, which is a 'pavement' of diamond stones. Otherwise multiple diamonds are simply called diamonds.
Coal has been called 'black diamonds'. This is probably because coal and diamonds are both formed from carbon.
They are called blood diamonds because the money made from them is used to fund wars and terrorist activities.
Diamonds are VALUABLE
Man-made diamonds are usually called man-made diamonds.