"Rainbow Rock"- the detail with the perspective on the side facing away is a nice touch. If only the same care had been put into making the gradient more organic. plus a small, selective color palate is much more attractive than an easy rainbow.
Copper sulfate crystals are among the easiest and most beautiful crystals that you can grow. The brilliant blue crystals can be grown relatively quickly and can become quite large. Here's how you can grow copper sulfate crystals yourself.