Gold and silver are commonly found in areas where igneous and metamorphic activity has occurred and are generally associated with silicic types of intrusives and Precambrian metamorphic rocks. When gold-bearing rocks weather, the liberated gold, because of its higher specific gravity, is mechanically separated from the accompanying lighter material and concentrated in the stream bottoms in the valleys. This type of mineral concentration is called placer.
In Kentucky, the geology is not favorable for the natural occurrence of gold or silver. Most of the surface and near-surface rocks are sedimentary, and there has not been any igneous, metamorphic, or tectonic event to allow the gold or precious metal to be concentrated in economic quantities.
The most common mineral mistaken for gold is pyrite, an iron sulfide, commonly referred to as "fool's gold." Another mineral that often confuses an amateur rockhound is muscovite, often called white mica. It is nonmetallic, but has a shiny luster, and when weathered it turns brownish gold. Small flakes of muscovite occur disseminated throughout some shales and sandstones in Kentucky. It is remotely possible that minute, noncommercial amounts of gold could be found in glacial outwash deposits along the Ohio River Valley. Some gold has been recovered from glacial debris in southern Ohio near the Kentucky border. If this gold exists in Kentucky, it was derived from sediments in the northeastern part of the United States.
Some silver was recovered from galena concentrates in the Western Kentucky Fluorspar District in the 1960's, but the amount was very small and uneconomic. The silver occurred in the crystal lattice structure of the galena.