Opal is a mineraloid gel which is deposited at relatively low temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, and basalt. The water content is usually between three and ten percent, but can be as high as 20%. Opal ranges from clear through white, gray, red, orange, yellow, green, shore, blue, magenta, rose, pink, slate, olive, brown, and black. Of these hues, the reds against black are the most rare and dear, whereas white and greens are the most common.
The opal is the official gemstone of South Australia, The Commonwealth of Australia and Nevada.
Opal is the traditional birthstone of the month of October.
Opals are said to contain the beauty and sparkle of all the other gemstones combined. The fiery, lustrous opals in these luxurious 2 5/8 Carat Opal and 1/3 Carat Diamond 14K White Gold Heart Earrings are beautifully complemented by halos of dazzling diamonds set in a heart themed design of gleaming white gold.