An engineer/prospector friend of mine will tell you that mineralization in the ground (especially in the mountains) will draw lightning. Also, the trees like Aspens will take up these same minerals and during the fall when the leaves change color, the trees with more of these minerals are generally more colorful than those with low levels of mineral uptake. When you are in areas suspected of gold and silver or other precious metals during the time of the autumn foliage, look for the more colorful leaves in the deciduous trees as these are more than likely to have more minerals beneath them than those which are more blandly colored. This works for the deciduous trees (those which drop their leaves each year) such as the Aspen tees. The evergreens will more often show signs of lightning damage. If you think about it in reference to the pdf file that Terry L Carter shared here, I believe you will see a correlation.
Thanks, Terry, for a very informative post.