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A simulation of a gemstone that is made of two or three layers of gemstone or glass that are cemented or fused together so as to appear as a whole natural stone.
The purpose is to provide a more attractive colour or a protective top surface (as for an opal).
They can be distinguished from genuine stones by several tests:
- by revealing a ring around the gridle, especially when immersed in water or certain liquids and then viewed from the side
- by having different specific gravity
- by microscopic examination
- by immersion in hot water or an organic solvent which will soften the cement and separate the layers
Such stones are sometimes called an ‘assembled stone’.