Opal is formed when an electrolyte (a positively charged water) rinses over sand stone causing the white silica in the sand to stack up like a crystal. So, most opal is white and most people think "all" opal is white. But, if other minerals are in the soil when the opal is forming, it will change colors. In fact, there are more than 23 colors of opal in nature.
There are 3 different types of opal: traditional opal; fire opal; and, black opal. These are classes of opal not colors. Each class of opal can be any one of the 23 colors.
Fire Opal has an orange color in the background that glows like embers in a fire when the sun hits it. It can be any color.
Black Opal is misnamed. It is never black, but it is so dark that it requires intense sunlight to shine down deep into it and reveal all the many colors hidden inside. It is more rare and, therefore, more expensive. It, too, can be any color.
Traditional Opal does not have orange in the background, so it is not a fire opal, and is not intensely dark, so it is not a black opal. It can also be any color.
On our site you will see 2 fire opals, white and green, and 2 traditional opals, blue and purple. There are several shades of blue opal in nature. We like the Caribbean Blue Opal because it is the darkest, richest blue of all the opals. This makes it really pop. The color shows up so well on skin that it will draw compliments every time you wear it.