Spelunker Potion

Ore and gems are the obvious part, but the tint covers most of what makes a cave worth entering: chests, Life Crystals and Life Fruit, pots, herbs and dye plants, and since a later patch, statues and paintings as well. A couple of oddities are on the list too, the Digtoise and the Huge Dragon Egg among them. In practice a whole exploration run collapses into looking at one screen and deciding whether to dig.

Pots, chests and crates all cough these up, and slimes occasionally drop one as a bonus. Most players end up with a supply they never crafted, which is worth knowing before you spend a Gravitation Potion's worth of ingredients on making them.

Four are missing: Crimtane, Meteorite, Obsidian and Hellstone. The Crimtane gap is the annoying one, since Demonite is covered and its counterpart is not, so a Crimson world gets less out of the potion underground. Meteorite and Crimtane at least emit their own light, which mostly covers the difference.

The yellow wash sits on top of whatever it marks, so ores you normally identify by color come out shifted. Cobalt reads turquoise, orichalcum reads red. Go by ore shape and by which layer you are standing in rather than by hue while the buff is up. The sparkle itself is easiest to pick out under Retro lighting.

The timer runs whether or not anything is nearby, so drinking one in an empty stretch of cavern burns the whole thing for nothing. A Metal Detector tells you if there is anything valuable in range first, which is the cheap way to decide. You can also cancel the buff early by right clicking its icon, worth doing when you surface with time left. The Spelunker Glowstick is the budget option, but it only sparkles over a rough area and has to be held or thrown to work at all, where the potion outlines the exact block.