The lava itself overrides the desert biome with it's own fishing loot tables. The native fish give very high cooked food stats. And consuming a Starlight Nautilus gives a one time 100 additional permanent max health.
Igneous resides in a larger Molten Quarry area at a distance of 1400 tiles from The Core. While the Ancient Forge scene, essential for crafting the Soul Seeker Pickaxe, can be found at a 1600 tile radius.
Otherwise, just take your time clearing out the mobs and use Scarlet Hoe to pick up the dangerous Magma Slime covering the ground.