(# bins = 10) of [Ni/OH], [Fe/OH], [Ni/CN], [Fe/CN], and [Ni/Fe] in log₁₀ for all comets with measured nickel and iron production rates to date. Ni, Fe, OH, and CN production rates were taken from J. Manfroid et al. (2021), R. Meier et al. (1998), D. G. Schleicher & D. J. Osip (2002), and P. Guzik & M. Drahus (2021). Ratios for 2I/Borisov are indicated by dashed black vertical line, and ratios for Hyakutake are indicated by red dashed lines. Metal/molecule abundance ratios for Hyakutake were derived from the geometric mean of the constrained range of production rate in Hyakutake. For Ni/Fe, an abundance ratio derived from the column densities is also shown.