Question: What kind of angle grinder blades are available and what type of blades are appropriate for the different types of stones?  Any recommendations regarding the purchase of an angle grinder?

Answer: (In answering this question, NWSSA member Tracy Powell had this response:)

There are two basic blade types: one is the bonded silicon carbide masonry disc that you can get in any hardware store, in 4- or 5-inch diameter. It is good for marble and anything softer (alabaster, limestone, soapstone).  The other is a diamond saw blade also in 4- or 5-inch (or even 7 or 10 inches, if you want) diameter that is made for cutting harder stones like marble, granite, sandstone, and basalt.  Of these, be sure you get one rated for dry cutting, and usually the turbo design is best.  You can use the diamond on all the soft stones too, but the bonded silicon will not cut hard stones.

As for grinders, so much depends on what you want to do with it.  If you are just getting started, and intend to expand your tool kit as you go, start with a single speed 4 1/2 inch grinder, and do not spend too much for it.  Makita, Milwaukee, Bosch, Black & Decker, Skil, Metabo, any of them will work, and there are a lot of other companies that make these grinders as well.  If you need the variable speed, going with the Metabo is a very good choice as it is currently considered the best.  If you want a general-purpose grinder that will last forever, the Makita 5 inch would be a good choice.