The dull green was followed successively by amber, white opal, blue opal, straw opal, sea-green, horn colour and various pale tints of soda-lime glass, ranging from yellow to blue.
The finest opal known is obtained in the Upper Cretaceous formation at White Cliffs, near Wilcannia, New South Wales, and at these mines about 700 men find constant employment.
Unscrupulous jewelers may pass off the total weight of the doublet as the weight of the stone and you will end up paying the opal's carat value for the total weight of the doublet, including the background stone or material.
For other forms of silica see OPAL and TRIDYMITE.
Hungary is the only country in Europe where the opal is found, namely at the famous mines of Vorosvagas in the county of SÃ¡ros, and at NagyMihaly in that of Zemplin.