Mineralogical Characteristics of Gold-mercury Mineral in the Davao Gold Placer of Mindanao Islands,Philippines and Its Prospecting significance

Mineral assemblage and mineralogical characteristics of gold-mercury minerals in the Davao Placer of Mindanao Islands,Philippines were systematically studied in this paper.Results show that,with the increasing mercury content in gold-mercury minerals,their reflecting power exhibits variations in the sequence of strong →weak → strong,in contrast to the decrease of mineral hardness.However,when the content of mercury reaches a definite proportion,especially when the crystal displays isometric crystal texture,its hardness increases.We also find that goldmalgam and r-goldmalgamite just occur as natural edge of gold-mercury mineral grains.Overall,mercury content gradually reduces from the edge to the centre of gold-mercury mineral particles,but that in the edge of grains is lower than that in the middle.With a combination of the analysis of metallogenetic background,this paper suggests that there are mantle-derived platinum and chromium deposits in the region,which are accompanied by ultramafic-mafic magmatism,and large and ultra-large scale gold,mercury-polymetallic deposits,as well as coastal placer of gold and platinum are also likely.