The Romans had been wearing opals for centuries and considered them a symbol of hope and purity while for the early Greeks they embodied the powers of foresight and prophecy. The more fancifully minded Arabs thought that opals must have fallen from heaven in flashes of lightning thus achieving their unique play of color or "opalescence". Amazingly this opal escence is a result of the 5-10% of water trapped inside the stone in which rows and rows of tiny spheres of silicon dioxide are arranged, diffracting light in a unique fashion to form wide spectrum of colors.

The official stones for those born in October are Opal and tourmaline. The physical structure of opal is unique. Tiny spheres of silicon dioxide form a pyramid shaped grid interspersed with water. Tiny natural faults in this grid cause the characteristic "play of color". The effect is similar to the rainbow colors displayed on a soap bubble, only that this is even more dramatic.
White Opals are commonly found and they vary widely in body color. Black is considered the most valuable as it accentuates the play of color. Fire opal like the yellow, orange or red, is often faceted and can resemble ruby. The rare of them all are the green and blue Opal.

The combination of body color and play of color, we are faced with infinite possibilities. So, pricing becomes very crucial and is very complex. Size is also a factor with the carat price for larger stones accelerating accordingly. The intensity of the play of color and the extent to which it covers the opal's surface also count.

Opal is occasionally cut with pieces of matrix - the host rock. This strengthens the opal and can also lend a more interesting appearance. The finest examples are Boulder Opal, which sometimes have an undulating surface of "hills" and "valleys". As opal is relatively soft and fragile it is often made into doublets or triplets - backed with plain black opal and fronted with clear quartz. These are ideal for opal rings or any piece that is likely to be receiving rough treatment.