I ignored lightning ridge as it is payable. More research.....
The earliest reports of precious opal in New South Wales refer to its occurrence in volcanic rocks. It was found in various localities, and, although attempts were made to exploit the discoveries, none were commercially viable. It was not until the discovery of high quality precious opal in sedimentary rocks in the area known as Wallungulla, now Lightning Ridge, and later White Cliffs, that the industry became established.