Simply put, gold comes from rocks. Huge rocks, in the form of mountains, are pushed upward by heat and pressure from deep inside the earth, and then the rocks are worn down by wind and water. Through water erosion, gold often becomes separated from the rocks, forming the rich placer deposits we're all looking for.
The kind of mountains that are most likely to contain gold have been subjected to earthquakes. Earthquakes produce "faults" which are places where the tension of the growing mountain became so great that part of the ground pulled away, leaving a long scar. Locating a fault line or "outcrops" (ordinary soil pockmarked with monoliths and low ridges of sold rock) are important to prospectors because these areas often point to places where minerals were thrust into the rip in the earth during a geological event. Normal erosion washes gold into waterways below, and gold being heavy, settles naturally along the way— on the inside edges of bends in the stream, in whirlpools where two creeks join, in and around natural obstructions such as rock crevices and boulders, in the roots of river plants and trees. Gold is often found mixed with concentrated strata of fine black or red sand. Black sands that are iron oxide are magnetic. Red sand is composed of tiny crushed garnets.
