Nylium

Nylium is a block that generates in the Nether. It has two variants: warped nylium and crimson nylium

Natural generation
Warped nylium generates in the warped forest biome, and crimson nylium generates in the crimson forest biome.

Post-generation
bone meal on netherrack placed next to warped nylium or crimson nylium will create more nylium of that type.

Obtaining
Nylium is mined fastest using a pickaxe, and will only drop itself if mined with a pickaxe.