Quote Originally Posted by Tokiko Mima View Post
Ok, what I mean is say you're casting teleportation circle, a spell that requires 1,000 gp worth of amber dust. You cast the spell, but what happened to the amber dust? Did it turn into normal dust, vanish, or teleport to somewhere else?

Obviously it's not still there on the floor, or the PC would scoop it back up for next time, defeating the point of their being a cost.
Most spells that use gem "dust" or metal "powder" involve scribing some manner of runes on a surface using that material. The material is then consumed by the energy of the spell using whatever cinimatics your DM sees fit. It might flare up in flames (natural colored or otherwise). It might pulse with light, and then fuse with the surface so that it looks like a paint or ink. It might do any number of things.

As for casting spells with costly materical components go, the easy way to do it is to just subtract from their gold total. The way it should go, however, is that the player has to buy/find/steal/etc the material, and then has x number of uses before they need to recharge. This is especially important when dungeon crawling. Jozan the Cleric leaves the temple of Pelor with enough silver powder to cast concecrate 5 times. While him and Tordek are in the Dungeon of Doom kickin zombies and takin names, he casts concecrate 5 times. He now can't cast concecrate any more times until he returns to the surface. That adds a degree of reality, and honestly isn't more difficult to track than potions that a player has. Make something like this.

25g in silver powder [] [] [] [] []
5000g in diamond dust [] []

Then just check the box when its consumed, erase the check when its replaced.