Stability
Fire opals are extremely fragile in nature, and unfortunately can be prone to crack within just a few months of wear. Check if the fire opal retailer keeps the stone for at least a year before selling it, and if they offer a guarantee against natural cracks and fissures. Most reputable dealers do!
Clarity
Look closely at the brightness or clarity of the fire opal. Are there any inclusions? If so then its possible the stones value will be decreased.The Cut of the Fire Opal
Cabochons with good color play are generally more valuable than faceted fire opals.Color
Color is one of the most important features in determining the value of a fire opal. Fire opals may run the gamut from deeper red, to orange, to yellow. Red stones are typically the most stable, though red-orange is a more desirable color. The more rich and lively the color, the better and generally the more valuable. Unlike standard opals, flashes of color play are not as common, so a fire opal without color play is still valuable. However, stones with red, orange, yellow, or even a blue color play flash in the light can be considered particularly valuable. You should check how the stone looks under both natural and unnatural (florescent) light in order to judge it's appearance.Size
The carat size of an opal can increase it's value, roughly the same as a diamond. Be sure that the stone has good depth and can withstand being set in jewellery.You may like: