Jamey and I have talked about the turquoise dyed magnesite and how close it looks to real turquoise nuggets. Here's a range of colors beyond just the typical turquoise blues.

This is Magnesite - Magnesium Carbonate which some vendors insist on calling "chalk turquoise." The black crevices are probably enhanced with something akin to shoe polish.

The store front shot shows a variety of man made "block" material. All kinds of imitation stone made entirely from plastic and color dyes. If you look closely you can see malachite, rainbow calsilica, turquoise, and coral colored blocks. The mirrors behind the shelving make it hard to get a good shot here.