There are a number of simulants of Diamond. These are either natural or man-made (synthetic) stones which, literally, simulate the appearance of diamond, and are sometimes used in their stead.
Synthetic simulants include glass, cubic zirconium (Cz)and moissanite.
The two most popular natural simulants are white zircon and white sapphire.
Natural white zircon (not to be confused with synthetic cubic zirconium - Cz) is a zirconium silicate and is colourless when pure.
Well faceted white zircon can rival diamond in its brilliance and fire, and is highly regarded in this respect. It was used exensively in the 19th century as a diamond replacement.
Zircon a hardness of 7.5 on the Mohs Scale and is most often faceted as a brilliant cut stone.
White sapphires are completely colourless sapphires. A sapphire receives its colour from the trace elements present within the earth when the crystal is forming.
White sapphires are quite rare as they are completely untouched by trace elements. White sapphires are excellent alternatives to diamonds as they are less expensive and very durable, at 9 on the Mohs scale of hardness.
They do, however, lack the brilliance and fire of diamond and should be cleaned regularly with a soft toothbrush to maintain their shine and sparkle.