An example of costume jewelry, where inexpensive materials have been used to mimick the real deal. Note the rounded facet edges and the bubble like inclusions in the larger stone below. These observations would lead to the gemologist to suspecting the stone being paste.
Costume jewelry is jewelery made from less costly materials such as plastics or wood and also inexpensive metals such as aluminum and copper. The stones used in this type of fashionable jewelry are usually pastes, cubic zirconias and other replacement stones. The genre is known to exist since the 18th century with many fashion houses having had - or still have - a line of costume jewelry. Some are highly collectible and high end. Modern costume jewelry can demand a high price although still considerably less than what it would cost if executed in precious metals and genuine gemstones.
Another meaning is jewelry made for a specific outfit or costume.