Zirconium dioxide jewellery. Like diamond, cubic zirconia has a cubic crystal structure and a high index of refraction. Visually discerning a good quality cubic zirconia gem from a diamond is difficult, and most jewellers will have a thermal conductivity tester to identify cubic zirconia by its low thermal conductivity (diamond is a very good thermal conductor). This state of zirconia is commonly called "cubic zirconia", "CZ", or "zircon" by jewellers, but the last name is not chemically accurate. Zircon is actually the mineral name for naturally occurring zirconium silicate (ZrSiO). Zirconium dioxide Zirconium dioxide (), sometimes known as zirconia (not to be
Natural History (Pliny) vases and other decorative objects. The account of magnetism includes the myth of Magnes the shepherd. Pliny moves into crystallography and mineralogy, describing the octahedral shape of the diamond and recording that diamond dust is used by gem engravers to cut and polish other gems, owing to its great hardness. He states that rock crystal is valuable for its transparency and hardness, and can be carved into vessels and implements. He relates the story of a woman who owned a ladle made of the mineral, paying the sum of 150,000 sesterces for the item. Nero deliberately broke two crystal cups