The Mariposa Geothermal System (MGS) is located 300 km south of Santiago, Chile, and has an inferred resource of 320 MWe. The field is outlined by a low resistivity MT anomaly with two lobes (or wings) that appear to relate to a clay cap associated to two principal upflow areas. The resource depth varies approximately 700 m to over 1000 m depending on terrain. The reservoir is likely contained within non-deformed volcanic rocks of the Campanario formation (Miocene-Pliocene) and folded and faulted volcaniclastic rocks of Curamallin formation (Eocene to Miocene). Structural analysis indicates locally a main control by east-northeast vertical structures with perpendicular extension, which intersect regional major NS lineaments. Geothermal manifestations (steaming ground and fumaroles) occur at four locations surrounding the MT anomaly, where the steep terrain cuts the margins of the clay cap. Gas geochemistry from these sources indicates a liquid-dominated reservoir with temperatures of > 250°C in the western part of the reservoir and lower temperatures (200-250°C) in the eastern lobe. There are no indications in the gas chemistry of acidic magmatic conditions. Drilling the MGS has proven to be challenging and of the three slim holes drilled to date, none have penetrated the deeper parts of the reservoir. Two wells measured temperatures over 200°C in the shallowest part of the reservoir. The wells were cored and have provided high quality geological information of the capping rocks of the reservoir. Plans for additional slim-hole drilling and large-diameter drilling into the deep reservoir, are well advanced as Magma progresses on developing this large, high quality resource.