Opal is a shiny, variegated stone that reflects light in many different colors. Generally white, orange, or black, all specimens have flecks of purple, red, green, and yellow dancing inside. Black opals of extraordinarily dark body color display the most brilliant flashes of color and are the most valuable form of opal. Transparent opals are the second on the scale of value, since many layers of color can be seen inside their depths.
Milky or white opals are the most affordable, but they tend to have diffused colors as a result of the light background. Water may compose up to 30% of an opal’s content, and drying out an opal may cause cracks to appear.
Preventing the formation of these fine, internal cracks, known as crazing, is believed to require the perpetual soaking of opal in a water or oil bath. Crazing does not usually occur in Australian black opal, but it is characteristic of Virgin Valley opals.
Virgin Valley Black Fire Opal is the state gemstone of Nevada. Opal is given and received as a symbol of hope, happiness, and truth, and it was described in medieval times as a cure for diseases of the eye.
Typically white, these stones are first soaked in sugar and then placed in sulfuric acid. The acid bath turns the sugar black, giving the stone a black body color appearance. Some hydrophane opals are dyed with a polymer or by a smoking treatment process.
As with sugar/acid, the goal is to make the opal look like a black opal. Opal is the anniversary gemstone for the 14th and 18th years of marriage.
