In the Motongkad prospect, East Bolaang Mongondow Regency, North Sulawesi Province, Indonesia, an epithermal gold mineralization occurred, hosted in andesitic-basaltic breccia, lava and tuff members the middle Miocene volcanic rock (Tmv). The Volcanic Rock is intruded by andesite dikes and contains fine quartz veins. Gold, silver, and pyrite found in the quartz veins.
This study consists of two main stages, field works and laboratory works. The field works were performed in whole area of the Motongkad prospect, where fresh and altered rock and mineralization samples were collected randomly, selectively, and systematically from outcrops as well as from a test pit. The laboratory works include petrography, X-ray diffraction (XRD), ore microscopy, and chemical analysis using the atomic absorption spectrometry (AAS) method.
The study area is arranged by three lithology units. Stratigraphically, the units are andesite rhyolite and tuff. The hydrothermal alteration in the study area are classified in five zones, namely: quartzsericite, quartz-sericite-clay, quartz-calcite-sericite-chlorite, quartz-calcite-sericite, and quartz-calcite- kaolinite. Motongkad prospect mineralization consists of two types, namely the vein type and the disseminated type. The ore minerals found in the Motongkad prospect are gold, pyrite, chalcopyrite, sphalerite, covellite, chalcocite, bornite and tennantite. We conclude that gold mineralization and its associated minerals in the Motongkad prospect are hydrothermal mineralization with epithermal characteristics.
Based on the results of mineragraphic analysis, there are two types of gold-bearing minerals found, namely native gold minerals and electrum, which are generally hosted by pyrite. Based on the distribution map of alteration and mineralization that has been made, it is recommended that the company wish to conduct mining with the highest gold content in the quartz-sericite and quartz-sericite- clay alteration zones, which are in the range of 0.83–1.07 g/t.

There is a sulfide mineralization vein type in the Cindakko area, Maros Regency, South Sulawesi. The results of mineralogical studies on the Cindakko prospects for sulfide ore mineralization are explained in this paper. Petrographic, mineragraphic, and XRD methods analyzed the mineralization and alteration samples from the research area. The results showed that the host rock mineralization is basalt, a member of the Baturappe-Cindakko Volcano from the Late Miocene age. The identified hydrothermal alteration mineral associations include quartz, chlorite, epidote, biotite, actinolite, and pyrite, generally formed in propyllitic alteration zones mainly characterized by chlorite. The analysis provides the occurrence of mineralization types: crustiform-banding quartz veins, vuggy quartz, and disseminated, contain hypogenic pyrite, chalcopyrite, sphalerite, bornite, and tennantite ores, and supergene ore minerals in the form of covellite. Ore textures recognized under a microscope are intergrowth, replacement, open-space filling, and exsolution. Based on the interpretation of temperature stability of hydrothermal alteration minerals, it is concluded that it was formed at approximately 200 to 320°C with the hydrothermal fluid pH almost neutral. The fundamental characteristics of hydrothermal alteration, ore mineral assemblage and texture, mineralization type, temperature range form, and hydrothermal fluid pH indicate that the mineralization in the Cindakko Prospect is an epithermal type.