Gold :
Because of the softness of pure gold, it is alloyed with silver, copper or palladium. The proportion of these other metals give yellow, white gold.
Without precision, the gold used in jewelry is 18 K, corresponding to 75% pure gold.
Carat :
The carat (ct) is a unit of mass equal to 2 g. Carat is used for measuring the weight of gemstones.
Choker :
A choker collar is a pearl collar where all pearls have the same diameter.