Meerschaum is a very rare mineral, a kind of hard white clay. Because of the light and pourous structure, the pipe keeps the smoke cool and soft. The pipe itself is a natural filter, which absorbs the nicotine. Because of this pecularity, these pipes slowly change their colors to different tones of gold and dark brown. The longer a pipe is smoked, the more valuable it becomes, due to the color change. Today, many old and rare meerschaum pipes have found a permanent place in museums and private collections.