Abstract
Many examples of oriented intergrowths are known.1 In some mineral occurrences it seems to be almost the rule. The well known ilmenite lamellae along the octahedral planes of magnetite have been a subject for discussion for many years. On the other hand, the oriented intergrowth of silver and dyscrasite, which seems to be quite common, has been described only recently.2 In other cases where oriented intergrowths might have been expected as in pyrrhotite and pentlandite none seem to exist. The case of tetrahedrite and chalcopyrite appears to be unusual. Oriented layers and crystal growth of chalcopyrite on tetrahedrite crystals have been mentioned frequently, but the microscopic oriented intergrowth of chalcopyrite and tetrahedrite has not been observed.
