Costume jewellery imitated precious gem jewellery. Large, single stone rings, hair ornaments and dangling clip-on or screw earrings were fashionable . A carat is one fifth of a gram - or 200 milligrams. A point is one hundredth of a carat - or 2 milligrams. As an indication, a one carat round diamond would be about 6.5mm in diameter.
Different stones have different densities.
For example, ruby and sapphire are more dense than diamond. Thus, a one carat ruby, or a one carat sapphire, is smaller than a one carat diamond. Gold In the United States and some other countries, the purity of gold is expressed in karats. The karat number refers to the parts of pure gold per 24 in the alloy. Many European countries mark gold with a three-digit number indicating the parts per thousand of gold in the alloy.