i recall reading that iridium actually has a slightly higher density (The Elements by Theodore Gray is good book like-like)

did a quick googs and
https://tinyurl.com/ycgzeyzg
says that both elements have swapped places for most dense a few times

@sonja: [...]but, with increased accuracy in factors used for calculating density X-ray crystallographic data yielded densities of 22.56 g/cm3 for iridium and 22.59 g/cm3 for osmium.