Ferroustry adds 8 new trees to aid in decoration. But that's not all, when the logs are blasted in a (vanilla) blast furnace, they will give back one of their respective material.
The trees do not spawn in worldgen, instead, they are crafted with 8 of the respective ore around any sapling or an alternative recipe that takes blocks instead.
The wood and materials that are made from the trees are 2x more blast resistant than normal wood, and fireproof due to their rocky origin.
version 1.3 brings 6 new trees: bismuth, copper, tin, aluminum, silver, and lead