Water flow might be the reason for those streaks but not so sure.
Thank you for introducing this contest to us :) @melinda010100
Water flow might be the reason for those streaks but not so sure.
Thank you for introducing this contest to us :) @melinda010100
@shasta posted a link above in her comment that explains 'desert varnish'
Hope to see some boulders from your part of the world!
I will try to post them soon :)