The gravels in contact with the bedrock or false bedrock base are often the richest. The same facts apply to the alluvial paystreaks that are formed on gravel bars; the lowest level of the gold-bearing gravel is normally the richest.

Geology is a science of general tendencies with frequent exceptions, not one of hard and fast rules that are always true and never vary. For almost every well-accepted rule of gold deposits, I can point you to a number of important exceptions.