Karat (abbreviated Kt or K) is the measure of the fineness of gold equal to 1/24 part. Pure gold is 24 karat gold, 18K gold is 18/24 gold, 14K gold is 14/24 gold, 12K gold is 12/12 (exactly half gold). Note that the term carat is used as measure of weight for gemstones.
A jewelry-making technique from Korea where 24k gold foil is fused to sterling silver.
from the Koroit mines in Australia. These are the hardest of the
opal types and often referred to as "Koroit picture opals"
because of the patterns.