Nature's own acrylic, a glob of hardened resin from one of the breu trees. There a lot of resin producing trees at Bosque Santa Lucia, but this sample came from a collector, who commercializes the product for caulking canoes and boats. The genus is Protium, but I don't know the species. There are some breu trees which produce resin of the color seen in the attached image. There are others which produce black resin.