yttrium aluminum garnet
Yttrium aluminum garnet is a man-made compound without natural minerals. Homogeneous body, high hardness. Before 1960, colorless and transparent yttrium aluminum garnet was used as a substitute for diamonds. However, its refractive index is too low, and the finished product is far less beautiful than diamonds. Since the later production of substitutes such as gadolinium gallium garnets with properties closer to diamonds, yttrium aluminum garnets have no longer been used to grind fake diamonds except as cheap substitutes for other gemstones.