A little experiment that I did. The values might not be correct.
Assuming an unchanged (one Earth) mass, these would be the characteristics of the Earth if it had the densities of the following materials:
Osmium, 22.61 g/cm3 - the densest element: Mean radius of 3980.65km (0.624 Earth), surface gravity of 2.56 G.
Gold, 19.30 g/cm3: Mean radius of 4196.3km (0.658 Earth), surface gravity of 2.31 G.
Iron, 7.874 g/cm3: Mean radius of 5657.87km (0.888 Earth), surface gravity of 1.27 G.
Steel, average density, 7.9 g/cm3: Mean radius of 5651.65km (0.888 Earth), surface gravity of 1.27 G.
Titanium, 4.506 g/cm3: Mean radius of 6814.79km (1.069 Earth), surface gravity of 0.87 G.
Aluminium, 2.70 g/cm3: Mean radius of 8083.48km (1.268 Earth), surface gravity of 0.62 G.
Carbon - diamond, 3.515 g/cm3: Mean radius of 7403.05km (1.161 Earth), surface gravity of 0.74 G.
Carbon - graphite, 2.16 g/cm3: Mean radius of 8707.64km (1.366 Earth), surface gravity of 0.53 G.
Water, 1 g/cm3: Mean radius of 11256km (1.766 Earth), surface gravity of 0.32 G.
And if it had the densities of the following astronomical bodies (but the same mass):
Venus, 5.204 g/cm3: Mean radius of 6495.39km (1.019 Earth), surface gravity of 0.96 G.
Moon: 3.34 g/cm3: Mean radius of 7530.09km (1.181 Earth), surface gravity of 0.71 G.
Mars, 3.9335 g/cm3: Mean radius of 7130.63km (1.119 Earth), surface gravity of 0.80 G.
Jupiter: 1.326 g/cm3: Mean radius of 10245.6km (1.608 Earth), surface gravity of 0.38 G.
Saturn: 0.687 g/cm3: Mean radius of 12756.5km (2.002 Earth), surface gravity of 0.24 G.
As I said, might not be correct, nor particularly scientifically plausible (there could be other factors at play on an Earth mass chunk of Osmium), but it's fun nontheless. :lol: