4 Olive Green Round Cubic Zirconia CZ Gem Stones 4mm. This is a new set of 4 olive green round cubic zirconia stones. Cubic Zirconia is a man-made composition stone. Cubic Zirconia is an inexpensive, high quality, and beautiful alternative to a genuine gemstone. This is why it is one of the major staples in the jewelry industry that at times may match or surpass the beauty of many expensive gemstones. The luster and brightness of these stones make them perfect additions to any jewelry piece. Each measures approximately 4 mm (1/8") in diameter.