make up roughly 59% of naturally-occurring tungsten. Slow-neutron irradiation could convert these isotopes into 185W and 187W, which have half-lives of 75 days and 24 hours, respectively, and always undergo beta decay to the corresponding rhenium isotopes. These isotopes could then be further irradiated to transmute them into osmium (see below), increasing their value further. Also, 182W and 183W, which together form 40.8% of naturally-occurring tungsten, can, via multiple neutron captures in a nuclear reactor, be transmuted into 184W, which can then be transmuted into rhenium. Osmium The cost of osmium as of January 2010 was $12,217 per kilogram, making it roughly twice the price of rhenium, which is worth $6,250/kg. Rhenium has two naturally occurring isotopes, 185Re and 187Re. Irradiation by slow neutrons would transmute these isotopes into 186Re and 188Re, which have half-lives of 3 days and 17 hours, respectively. The predominant decay pathway for both of these isotopes is beta-minus decay into 186Os and 188Os. Iridium The cost of iridium as of January 2010 was $13,117/kg, somewhat higher than that of osmium ($12,217/kg). The isotopes 190Os and 192Os together make up roughly 67% of naturally-occurring osmium. Slow-neutron irradiation could convert these isotopes into 191Os and 193Os, which have half-lives of 15.4 and 30.11 days, respectively, and always undergo beta decay to 191Ir and 193Ir, respectively. Also, 186Os through 189Os could be transmuted into 190Os through multiple neutron captures in a nuclear reactor, and subsequently into iridium. These isotopes could then be further irradiated to transmute them into platinum (see below), increasing their value further. Platinum The cost of platinum as of October 2014 was $39,900 per kilogram, making it equally as expensive as rhodium. Iridium, by contrast, has only about half the value of platinum ($18,000/kg). Iridium has two naturally occurring isotopes, 191Ir and 193Ir. Irradiation by slow neutrons would transmute these isotopes into 192Ir and 194Ir, with short half-lives of 73 days and 19 hours, respectively; the predominant decay pathway for both of these isotopes is beta-minus decay into 192Pt and 194Pt. Gold Chrysopoeia, the artificial production of gold, is the symbolic goal of alchemy. Such transmutation is possible in particle accelerators or nuclear reactors, although the production cost is currently many times the market price of gold. Since there is only one stable gold isotope, 197Au, nuclear reactions must create this isotope in order to produce usable gold. Gold synthesis in an accelerator Gold synthesis