The Barton garnet deposit contains large garnet crystals (2.5--25 cm) disseminated through a gabbro-derived garnet amphibolite. These crystals are characterized by two sets of parting planes which intersect at about 80¿ and have a constant attitude throughout the amphibolite. The results of X-ray diffraction studies on the parting planes of the garnet crystals by the back-reflection Laue method and by X-ray diffractometry show that the parting-plane sets are not crystal-lographically controlled by the lattice of the garnet and that the garnets are not oriented in the amphibolite. Each parting set in the giant garnets and its corresponding parallel joint set in the amphibolite matrix are interpreted as brittle fractures which developed in response to a discrete tectonic episode.