October Birthstone

In the middle ages, it was believed that opal could make the wearer invisible.
The name opal derives from the Greek Opallos, meaning "to see a change (of color)." Opals range in color from milky white to black with flashes of yellow, orange, green, red, and blue. An opal's beauty is the product of contrast between its color play and its background. Opal is a formation of non-crystalline silica gel that seeped into crevices in the sedimentary strata. Through time and nature's heating and molding processes, the gel hardened into the form of opals. The opal is composed of particles closely packed in spherical arrangements. When packed together in a regular pattern, a three-dimensional array of spaces are created that give opal its radiance. 
Opal is available in almost every shade of each color. From translucent to transparent and milky white to dark black, opal exhibits all the colors of the rainbow. This vivid-colored birthstone is said to impart hope, confidence, and harmony, to the people born in October.