October Birthstone: Opal Facts and Tips

Opal is known as the October birthstone, and also marks the 13th wedding anniversary.
Most opal is 50-65 million years old, dating all the way back to the Cretaceous period. It was formed from decomposing rocks mixed with ground water which formed a silica gel that collected and hardened in underground cavities. Opal's chemical formula is SiO2 .nH2O.
There are two types of opal; common and precious. The way the silica particles form determines which type it is. In precious opal, silica particles are packed in regular rows and layers. Moving the stone causes light to diffract, or split, as it grazes the opal surface. This light diffusion shows iridescent flashes of green, blue, aqua and sometimes yellowish or red colors which are referred to as "fire".

This gemstone actually contains up to 30% water, so it must be protected from heat or harsh chemicals, both of which will cause drying and may lead to cracking and loss of iridescence. Opal must also be guarded from blows, since it is relatively soft and breaks easily.
Ancient monarchs treasured Opals, both for their beauty and for their presumed protective powers. They were set into crowns and worn in necklaces to ward off evil and to protect the eyesight. These gemstones were also ground and ingested for their healing properties and to ward off nightmares.

The Opal was called "Cupid Paederos" by the Romans, meaning a child beautiful as love.