This is the closely-grained burl joint between the stem and roots of the White Heath, a tree found on the hillsides of mainly Mediterranean countries. Underground, this burl protects the briar wood, which is tough,
close grained, porous, and nearly impervious to heat. Good briar is hard to find. The larger shrubs take a long time to mature...and the older the shrub the better the briar and thus your pipe. The most suitable root may
be 80 to 100 years old, and the finest pipe briar may be from a shrub over 200 years old... aged and mellowed by time.