My favorite stone to imitate is turquoise. I love how it can look so much like the real thing yet not have the same weight that the natural stone has so is more comfortable to wear.
Here are a couple of sample pieces we created using this technique. The one below has the "turquoise" embedded into a focal pendant and strung with "turquoise" beads each formed by hand. The square beads in chili red were also hand crafted from polymer clay.
This collar style necklace is one of our favorites and even though it looks heavy, it is quite lightweight due to using the polymer clay rather than the real stone. The collar piece is strung with our own rondelles in black (see our tutorial we posted earlier) and some of our new handcrafted heishi beads using the same turquoise.