Meerschaum is a soft stone that is mined within a 4 mile radius of Eskishir Turkey. Meerschaum actually is a German word meaning sea foam to describe how deposits would break off of the sea floor and drift onto shore to be gathered and carved into jewelry, statuettes, or whatnot. Today these pipes are hand carved and priced according to size, quality of stone, cleanliness of carving.
The quality of stone is judged shortly after being mined and is sorted according to size, color, and weight. After being sold in lots the carvers receive the stone and begin searching for imperfections as well as determine what shapes would be best represented by each particular stone. The finished pipe should have a translucent white finish with no chalkiness although sometimes the bees wax will yellow on some pipes.
Clean carvings are most desirable and directly influence the collectability of the pipe. The carving should be symmetrical, well balanced, and life like. In face carvings the single most important feature is the eyes. Does the carving look as if the character can wink at you? As with any artwork, each pipe should be distinctive, defined, and obvious as to what it portrays.
One of the greatest mysteries in pipe smoking is how meerschaum pipes color. Industry experts are divided as to how this occurs but the most general concessions is that it is a reaction between the smoke, heat, and wax finish all being filtered by the stone in the pipe. Hand oils have a minimal impact on the finished look but sometimes finger prints can mar the wax during coloring. Dirt will also dull the effect and the pipe should be kept clean from dust and debris. On a side note I have found that if one keeps the meerschaum pipe reamed it seems not only to smoke better but also color better.