In search of the lost link: the fascinating platinum host rock of Chocó, Colombia

Abstract

In Colombia, after nearly 500 years of the quest for the platinum source rock, a remarkable discovery of a fossiliferous limestone with gold and platinum now resides under the watch of the Geological Survey's Museum in Medellín, registered as RS 2.2.1.1.3. Platinum group minerals, long sought after in Colombia's placer deposits since the 19th century, typically found in the form of nuggets, have received special attention due to the missing link that exists between authigenesis in mafic/ultramafic rocks to detrital alluvium associations. Consequently, this finding unveils an entirely new environment hosting platinum. In this article, we delve into the historical context and the heritage value of a sample boasting 300 g/t of platinum and 33 g/t of gold, embedded in a dolomitized biosparite. Various analyses, encompassing atomic absorption spectroscopy, X-ray diffraction, micropetrographic characterization, and scanning electron microscopy coupled with energy-dispersive spectroscopy, were performed on the sample. The sample baffled experts due to its unassuming sedimentary rock appearance and the unusual circumstances of its arrival at the museum. Hence, it stands as one of those uncommon scientific curiosities with an unforeseen origin, accessible only through a stroke of chance and an unbiased perspective regarding its origin. Beyond its historical and geological significance, this specimen, safeguarded within the museum's collection, encourages education and awareness regarding geosites, advocating for the preservation of one of the planet's most biologically diverse regions, where platinum was first discovered.