October has two birthstones, opal and tourmaline.
Opals are a product of seasonal rains that soaked dry desert areas, the rains soaked into ancient underground rock washing out silica and carrying into cavities in the rock. During dry periods the water evaporates and leaves microscopic grains of silica that layer in the cavity creating the opal. Opal can contain up to 20% water.
Opal is known for its unique flashes of a rainbow of color, called play of color. Opals consist of microscopic spheres of silica stacked in a grid like manner that when light waves travel through the silica they bend causing the flash of color. The color depends on the size of the silica sphere, a 0.1micron sphere creates violet, a 0.2micron sphere creates red, other colors are from the sizes between violet and red.
Gem opals are divided into five categories, white opals, black opals, boulder opals, fire opals and crystal opals. Opals are a relatively soft gemstones and most be worn with care.
White opals are semi-translucent or translucent play of color against a white or grey background color (body color). Black opals are translucent to opaque with a dark or black body color. Boulder opals are translucent to opaque with the play of color against light to dark background and the surrounding rock called the matrix. Fire opal is a transparent gem with yellow, orange, red or brown solid body color without any play of color. Crystal or water opals are transparent to semitransparent with a clear body color and show exceptional play of color.
Opal comes from the Latin opulas meaning precious stone and in ancient Rome it symbolized hope and love. In 75AD Pliney observed the kaleidoscopic of color this gem encompassed the red of ruby, the green of emerald, the yellow of topaz, the blue of sapphire, and the purple of amethyst.
The ancient Greeks believed that opals gave their owners the gift of prophecy, protection from disease, and bring the wearer universal good will. Arabic legends have opals fall from the sky in flashes of lightning. Europeans have long considered opals symbolize hope, purity and truth. At one time opals were considered to preserve the life and color of blonde hair. The notion that opals are unlucky for anyone else to wear opals besides those born in October comes from a novel written in the 1800’s, Anne of Geierstein by Sir Walter Scott, not from any ancient belief or experience. On the contrary, throughout history opal has been regarded as the luckiest and most magical of all gems because it can show all colors.