The first rule of opal mining is to dig near someone who has already found opal. Miners in Australia work multiple claims.
Loose opals on the surface, called floaters, are rarely found these days. After a hundred years of miners looking for opal, they’ve all been found!
Today, miners search for “slips” vertical opens in the ground that let ground water seep into the earth. They use dousing to find these slips.
Open cast, also known as surface mining, finds opals at a shallow level. Boulder opal miners in Queensland dig for the shallow levels, for example. At Mintabie, miners use bulldozers to dig swathers 100 feet deep.
However, underground mining is the norm at Lightning Ridge, Coober Pedy, and Andamooka, which have seam opal.