"But gold remains an enigma." Indeed, there are problems in observations with r-process and s-process answers to the elements documented in astronomy. The critical assumption is BBN and the origin of pristine, primordial gas clouds (the original clouds that formed shortly after BBN ended) and Population III stars. Apparently none have been measured and observed yet but observations of gold show problems ongoing with r-process. Some other reports on this interesting problem,
https://phys.org/news/2020-09-elements-neutron-stars-contribute-gold.html, "New discoveries are to be expected from nuclear facilities around the world, including Europe, the U.S. and Japan, currently targeting rare nuclei associated with neutron star mergers," she said. "The properties of these nuclei are unknown, but they heavily control the production of the heavy element abundances. The researchers concede that future research might find that neutron star collisions are more frequent than the evidence so far suggests, in which case their contribution to the elements that make up everything from mobile phone screens to the fuel for nuclear reactors might be revised upward again. For the moment, however, they appear to deliver much less buck for their bangs.”
The Origin of Elements from Carbon to Uranium,
https://ui.adsabs.harvard.edu/abs/2020arXiv200804660K/abstract, August 2020 “ABSTRACT To reach a deeper understanding of the origin of elements in the periodic table, we constructGalactic chemical evolution (GCE) models for all stable elements from C (A=12) to U (A=238) from first principles, i.e., using theoretical nucleosynthesis yields and event rates of all chemical enrichment sources. ...• Our purely-theoretical models allow us to discover consistencies, and inconsistencies, that arise only by considering all the elements together. For example, we find that silver is overproduced by a factor of 6, while gold is underproduced a factor of 5 in the model (Fig. 32). It would be worth revisiting the nuclear reaction rates relevant to these elements. It is also necessary to increase the samples of observational data, in particular with Hubble Space Telescope.”