What is the fineness grade of the gold found in the main tertiary channel gravels of the Sierra Nevada of California, and briefly describe why it is this grade.
NO COPY AND PASTE ANSWERS, PLEASE.
ANSWER: The grade of the gold found in the tertiary channel gravels of the Sierra Nevada of California is 900. The lode mines of the area have gold deposits that are much lower in grade, due to the silver that is found with it. It is thought that the percolation of the water over and around the placer gold deposits leaches the silver out of the gold over time, leaving the placer deposits of a finer grade of gold than the lodes they come from.