This might be of interest to you thinking about adding weight to your locomotives or rolling stock. It's part of a list I found on the web, I filtered out everything except metals with densities heavier than lead. Don't remember what the units are.
Of the metals shown, it looks like tungsten and gold are the only ones that are a) available and b) don't glow in the dark. Either one is not quite twice as dense as lead.
Bill K
Iridium 22.2
Platinum 21.3
Plutonium, alpha phase 19.4
Gold, Pure 19.3
Gold, cast-hammered 19.3
Uranium D38 19.0
Tungsten 18.8
Uranium 18.7
Gold Coin (US) 17.2
Tantalum 16.6
Mercury 13.6
Thorium, Ind. melted 11.6
Lead 11.4
Of the metals shown, it looks like tungsten and gold are the only ones that are a) available and b) don't glow in the dark. Either one is not quite twice as dense as lead.
Bill K
Iridium 22.2
Platinum 21.3
Plutonium, alpha phase 19.4
Gold, Pure 19.3
Gold, cast-hammered 19.3
Uranium D38 19.0
Tungsten 18.8
Uranium 18.7
Gold Coin (US) 17.2
Tantalum 16.6
Mercury 13.6
Thorium, Ind. melted 11.6
Lead 11.4