All About Opals

Opal is the birthstone for October and the anniversary gemstone for the 13th year of marriage. That is ironic sense many believe that opal is bad luck. Queen Victoria intervened in the near destruction of the 19th century Opal market when the writer Sir Walter Scott started a superstition that Opals were bad luck for people not born in October. In one of his novels the heroine owned an Opal that burned fiery red when she was angry and turned ashen gray upon her death. Queen Victoria finally dispelled the curse by giving Opal Jewelry as gifts at a royal wedding. In the early 1900’s the Diamond Commission resurrected this rumor because Opals were gaining in popularity over diamonds for engagement rings.

Opal is mainly from Australia, but it also comes from Mexico, Peru, Brazil and Indonesia. We will concentrate on Australian opal because that is what we feature in our entire collection of one of a kind pieces. Australian opal comes in three varieties, Crystal Opal, Boulder Opal and Black Opal.

The Black Opal mining fields of Lightning Ridge and the majority of Australia’s Opal fields are located in a geological phenomenon called ‘The Great Australian Basin’. The Basin was formed from sediments of a large inland sea that existed over 140 million years ago. 125 million years later, sandstones were deposited by waterways over the top of these sedimentary rocks. Eventually these younger rocks weathered, and their silica filtered down to cavities in the older host rock in the form of a gel. The silica gel hardened forming around a nucleus, creating the Opals characteristic regular spheres and voids. It’s the diffraction of light through these transparent spaces that produce Opal’s brilliant play of colors.

Black Opal is only found at Lightning Ridge in New South Wales, Australia. This magnificent gemstone is the most valuable form of Opal. Its dark background color, usually black or gray, sets the spectral colors ablaze much like a storm cloud behind a rainbow. Black Opal is so valuable that even wafer thin slices are made into doublets or triplets to give them enough strength and depth to set into gold rings and other jewelry items. It is easy to detect Black Opal from other varieties because of its unusual black “Potch”, the host rock on which the Opal formed. Black Opal is the most valuable and beautiful type of opal. The depth and variety of colors is unsurpassed by any other gemstone.

Boulder Opal is found in several mines through out Australia. The main ones are Coober Pedy, Andamooka and Mintabe. It’s very easy to distinguish Boulder Opal from other varieties; it always has ironstone on the back of it. A brown boulder rock that is part of the stone and acts as a natural background to lock in all of the spectacular color. Boulder opals are usually a blue/green color with sparks of red, yellow, orange or purple.

The third type of Australian Opal is crystal opal. It has a white body with a rainbow of complementary colors throughout. Crystal Opal is transparent and is pure opal (hydrated silica.) It typically has sharp clarity of diffracted color visible from within and on the surfaces of the Opal. When held out of the direct light, Crystal Opal displays some of the most intense Opal color. This is the type of Opal used in Opal inlay Jewelry, which has the base of the setting blackened before the precision cut crystal Opal is set into it. 

Opal is a fragile stone because all opals contain water. The content varies but it can be as much as 30%. In can happen in the course of time, the stone loses water, cracks and the opalescence diminishes. This is why Big Island Jewelers lets a loose opal sit for years before we set it in to a piece of jewelry so that any water loss will happen before you purchase it. Opal is sensitive to pressure and knocks

Some of our One of a Kind Opal Pieces: