Geological Appraiser

A spell's mana value is determined only by its mana cost. Ignore any alternative costs, additional costs, cost increases, or cost reductions.

If you can't cast the discovered card (perhaps because there are no legal targets for the spell), you'll put it into your hand.

If you discover an adventurer card, split card, or modal double-faced card, you might be able to cast that card with either set of characteristics depending on the effect's discover value. For example, if you discover 4 and reveal Galvanic Giant (an adventurer card from Wilds of Eldraine with a mana value of 4), you could cast Galvanic Giant, but not Storm Reading (its Adventure, which has a mana value of 7). If you discover 7 and reveal Galvanic Giant, you could cast either Galvanic Giant or Storm Reading.

Geological Appraiser's triggered ability triggers if you cast it from any zone. It doesn't trigger if you put Geological Appraiser onto the battlefield without casting it.

You exile the cards face up. All players will be able to see them.

Some spells and abilities that cause you to discover may require targets. If each target chosen is an illegal target as that spell or ability tries to resolve, it won't resolve and you won't discover.