As I recall (away from my PHB right now), there's a short list of materials that includes silver, stone, iron and wood, and you can transmute any one such substance into another on the list.
This. Here is the precise list of allowed materials:
Wood
Stone (not gemstones)
Iron
Copper
Silver
You can transform any
one object made of one of those materials into another material on that list. So no rope, string, etc. Not even lead. You therefore cannot produce a bunch of silver coins. Depending on how you interpret duration, you
may be able to have a 5 at once (briefly).
Duration is described in a way that makes it unclear as to whether it functions like a concentration spell with a duration of up to 1 hour, or whether it has a concentration duration, but with a minimum of 1 hour even if you cease concentrating. Given that the minor conjuration feature of the conjurer is superior in my estimation, I'm prone to go with the more liberal latter interpretation.
Since it requires (as I read it) a minimum of 10 minutes to transmute something, and since you can't concentrate on more than one thing at a time, you could spend 50 minutes to have 5 objects (of no more volume than 1 cubic foot each) transmuted at once, with one of the first 4 changing back every 10 minutes, and the final one lasting until you lose concentration. It is worth noting that it doesn't say that the effect ends if you use it again, so concentration is the only limitation on multiple effects.
The ways to use the effects of minor alchemy seem rather limited compared to minor conjuration (which essentially lets you conjure most items of equipment you might need with a single action, such as a crowbar, shortsword or mace, a grappling hook, a coil of rope (depending on how liberal your size interpretation is) and many more (though only one at a time). Therefore I feel it's appropriate to use the most liberal interpretations of minor alchemy to allow it to catch up. So, as someone posted in this thread over on the Wizards forums, stone could include pumice (turn the bars of your jail cell from iron to pumice and smash them), chalk (for writing), or soapstone for carving (wood would also work for carving).
It seems to me that it's must useful functions are turning a hard or tough material into something brittle or easily destroyed, or something you can shape more easily. Making a crowbar out of a stick is another good example.
Given that most of the 2nd level wizard features are very useful on a regular basis, it definitely needs either a bit of a boost or the most liberal interpretation possible of each element.
Anyone interested in trying out their RAW optimization cheesiness powers to come up with ways that it could be used beyond what I described? I'd appreciate the added efficacy of it.
