Wow! That's it...you got the thing with the rich color beneath and the dull reflections on the surface.
Thanks, John. I do like to paint rocks and water. Did you remember the painting of the logs under water? I think I saw that one but I can't remember who the artist was either. Here is one I did find: http://billcone.blogspot.com/2012/10/sonoma-plein-air.html
I think it was by Marc Hansen, from a couple years back.
I think you will be well prepared. Lovely study.
Thank you for the comment.
Rocks always present a challenge... until one approaches them the way a geologist would... they are layered planes.