This paper is an attempt to elucidate the possible origin of massive sulfide occurrences of Bagacay Mine in the light of new information unraveled by recent mining activities. The opening of the Guila-Guila orebody and deeper diamond drilling has made possible for the first time a better observation of various rock types and distribution of mineralized zones. Earlier ideas and theories on the origin of these deposits have been considered in this paper since their interpretation and inferences are also based on valid earlier field work and mineragraphic studies.

Bagacay Mine is a distinct massive sulfide deposit for the following reasons: (1) It is the only known copper deposit in the Philippines containing complex massive sulfide and carbonaceous ore with relatively high copper grade in a volcanic setting; (2) It is the only copper prospect in Samar Island which has proved to be of economic importance so far; and
(3) It is an iron prospect that has tumed out to be a copper mine.