Identification of opal jewelry

Opal according to its color can be divided into black opal, white opal, yellow opal, of which the highest price the black opal. In order to lower the price of white or yellow opal improve grades, someone on the use of artificial means to make it change color, become "black opal" in order to seek Gregory. The main method is to use candied or injected plastic, so that white opal black. Identification method is that, after injection of Opal candied or proportion significantly different in the water test, the specific gravity value becomes lighter. It can also be used to test the heated needle injection Opal, Opal natural hot needle into, injection Opal able headlong, and will produce odor after molten plastic.