There are two kinds of sodium lights: Low Pressure (LPS) and High Pressure (HPS). These lamps are mostly used for street lighting as well as industrial uses. The lamp works by creating an electric arc through vaporized sodium metal.
Enhanced Turquoise. Enhanced Turquoise is a natural stone that has only been treated with either chemicals and heat, or just heat to enhance the color and harden the stone. This type of treatment keeps the color from fading over time and makes more of the harder turquoise available for the market.
What Paula says is right all turquoise has to be stabilized as the stone is soft and brittle. stabilizing is accepted and does not interfere with the cost. Enhancement though is a different story because if the stone is actually dyed than it is no longer natural. You have to find out what kind of enhancement has been done.