Diamond-Like Cubic Zirconia, the original Diamond simulant. Scientifically created in the 1930s for use in optics, it quickly became the major Diamond look-alike, its clarity and glitter making it difficult to distinguish at a glance from the real thing. It has a hardness of around 8 on the scale, harder than most gemstones though not at all on the level of Diamond hardness.
(Soon after its Diamond appearance, when polished and cut, became apparent to insiders, some operators moved a quantity of the synthetic into India, historically a land where Diamond is much appreciated, and defrauded many dealers throughout the country. The episode was vividly remembered some decades later.)

The pendant is Sydney-crafted in solid 9ct Gold, 1.4 grams of 9ct Gold used. The Cubic Zirconia is professionally bezel-set in Sydney.