Here are some interesting facts about the birthstone for October:
1. Opal is a sedimentary stone that is formed from a solution of silicon dioxide and water. As water runs down through the earth, it picks up silica from sandstone, and carries this silica-rich solution into cracks and voids that are caused by natural faults or decomposing fossils. As the water evaporates, it leaves behind a silica deposit. Then, under the proper conditions, water percolates through the earth, becoming rich in dissolved silicates. When water enters a cavity, it deposits the silicates as microscopic spheres, forming opals.
2. The millions of sub-microscopic spheres of silica that are packed together to make an opal range in size from about 0.1 to 0.2 microns (0.1 microns is one ten-millionth of a meter).
3. The gaps between these tightly packed spheres bend and split rays of light that hit the surface of the opal. This is called diffraction and it’s what creates the gorgeous “play of colors.” Basically, opal is composed of tiny spheres that diffracts light and brings the fancy spectrum of colors.
4. Opal is not extremely hard. It is a delicate stone measuring 5.5-6.5 on the Mohs Hardness Scale.
5. There are different types of opal that have different base colors (white opal, black opal, fire opal, boulder opal and opal doublets).
6. Ancient Greeks believed that opals gave the wearers the gift of prophecy and guarded them from disease.
7. The ancient Greeks also believed that opal came from the tears of Zeus, the God of lightning, after winning a battle against the Titans. His tears turned into opal when they landed upon earth.
8. In the United States, opals are mainly found in Nevada, Oregon and Idaho, but Australia is where opals are mainly found.
9. Andy Warhol became obsessed with opals and became an avid collector. In 1977 he exhibited his photographs of opals taken through a microscope.
10. Another fan of opals was Elvis Presley. He had a vast collection of jewelry and opals were a favorite.