I want to go on record as saying, "I am fine with buying fake Turquoise. As long as I know what I am buying." No one likes to be the subject of Tom Foolery—no matter how genuine he seems.
The Egyptians were the first to produce imitation turquoise glazed earthenware. Glass and enamel have been used, and today ceramics, porcelain, plastics, and various other materials have been used to imitate turquoise. Most commonly, dyed howlite and magnesite have been used to imitate turquoise.
It is difficult to tell the difference between a good fake and the real thing. However, I have learned a few tricks in my years of dealing with rocks and minerals; here are some tips:
1. Look for color inconsistencies. Turquoise does have variegations in color, BUT dyed stones will have telltale lines, where the dye has collected in the natural cracks of the stone.
2. Tap it on your teeth. It sounds weird but it works. Turquoise has a dull density when you tap it on your teeth. If the stone in question feels too much like plastic (dull soft) or glass (sharp dense) to your teeth, be sure you know what you are buying. (The best thing is to train your teeth – get a piece of turquoise, a piece of amber, and a piece of quartz to tap. You will be able to tell the difference. The amber will tap like plastic or resin. The quartz will tap more like glass.)
3. Ask. A good dealer, artisan, etc. will know the history of the turquoise they are selling. Their reputation is at stake, and they don’t want you to walk away unhappy.
4. Keep your receipt. At the very worst, you find out you bought bogus turquoise. RETURN IT!