Meerschaum . . as natural blocks is

• a soft, white, heat-resistant mineral
•  a hydrous magnesium silicate H4Mg2Si3O10 and used for tobacco pipes, etc. (1)
•  fossilized remains of the sea-animals that lived millions of years ago,
•  mined from 250 to 300 feet under the ground surface, in irregular forms and sizes,
•  offers as a pipe " cool " and " dry " smoke with a flavour which is unrivaled by any other pipe substance, and
• its high porosity acts as "natural filter" allows to absorb the nicotin. . that is why it takes a rich brown color as used 
  (1) Webster's New World Collage

The best quality of meerschaum in blocks are extracted nowhere in the world but only in Turkey. 
Whereas the lower qualities do not absorb the nicotin as the above ones. Though the pressed meerschaum do not absorb at all.

About 200 years ago, the first ever meerschaum-pipe was carved by a certain shoe-maker called Kovacs in Budapest. Before than nobody knew about this mineral, which could be excellently carved to make pipes.
Eversince "carving" has become almost an art.