Crystals of zeolites (phillipsite) form in the red-clay as radiate, nodular groups.
There is a pair of large nodular sesamoids behind the metacarpo-phalangeal articulation, and a single large transversely-extended sesamoid behind the joint between the second and third phalanx, called the " navicular bone."
Thick, with nodular segregations and abundant cavities which are often lined with zeolites.
It is generally nodular, and forms rounded or highly irregular masses which may be several feet in diameter.
Even the growth of the well-known nodular incrustations in iron pipes is much reduced by sand filtration.