According to gold mining expert R. J. Forbes, there exists no clear record of ancient prospecting methods. However, it seems likely that one of the most obvious techniques, looking on the ground, was employed to search for items of interest. The ground is a treasure trove of artifacts that would have been useful in antiquity. Many mineral pieces and, indeed, precious metals that were worked into useful or decorative objects and now have pride of place in museums presumably were found lying on the ground.
Prospectors in antiquity knew that to discover gold you had to have a keen eye. Gold mining expert John Arthur Phillips once advised gold hunters to take a leaf out of the ancients' books and examine the sands of rivers, streams and eddies very carefully to try to discover fine, scaly particles of gold. This would indicate whether an area was rich in gold or not. A further tip was to observe sections of open rock in the area, looking for auriferous, or gold-bearing, quartz.
The ancient Egyptians taught the Romans about gold prospecting. This included how to process reef gold with a regime of pounding, grinding and washing. Reef gold is usually embedded in a mass that comes from sections of rock or other material that differs from the nearby strata, or rock layers. Pounding helps to loosen extraneous material from the mass. Grinding breaks the rock down into nuggets, which can then be washed.
Geobotanical prospecting is using a knowledge of the geographic distribution of plant species to help determine what minerals or precious metals lie in the ground beneath them. An early form of the practice was known at least 1200 years ago. Chinese scholar Tuan Chhêng-Shih advised that in a mountain area where grows the tshung plant, a type of onion, silver would be found beneath it. To find gold, you would look for the hsiai plan, a type of shallot. Where you observed tree branches drooping, it was a sign that precious jade was to be found below them.