A variety of the mineral andalusite with the chemical composition Al2SiO5 with inclusions of graphite giving a cross shaped pattern. The usual theory for the cross shaped pattern is that there is a selective attachment of impurities at the rapidly growing corners of andalusite crystals. Primarily of graphite the concentrated impurity deposit forms a re-entrant as it is absorbed by the growth of the andalusite porphyroblast. The growth then repeats itself, creating a featherlike pattern of graphite along four radiating arms.
In the world of crystal healing it is said to be a protective stone, protecting you from negative energies and preventing your energies from getting drained.
Price if for one polished pebble approx 2cm in length.