Etched lumps of transparent gemmy obsidian (originally mistaken for "tektites") embedded in red Cretaceous marls of the Miraflores Formation near Miraflores hot springs. Exact locality is still a secret known only to the indigenous prospector who found this deposit. Analysis shows that orange microcrystal inclusions in this obsidian are spessartine.
The Miraflores Formation is better known as a source of Cretaceous fossils, including the stromatolite beds much used for lapidary slabs, cubes, eggs and spheres (which often appear at northern hemisphere gem and mineral shows misrepresented as "Precambrian stromatolite").
