GURPS Magic - Creating gemstones
 

In GURPS Magic, Earth to Stone explicitly say it can’t create gemstones, but allow for creating basically any “simple” metal like bronze (actually an alloy) or iron. There are long discussions on this board about the meaning of “simple metals” (is gold valid? What about mercury? And steel?), but I am not interested this topic

What I am looking for is the reasoning for why gems were excluded, and what would a spell to create them be like - is there even an official one?

Re: GURPS Magic - Creating gemstones
 

I think the purpose is to keep people from creating a lot of valuable material and short-circuit any adventure where there's a reward. If you can create a cubic yard of diamonds then the economy will very quickly be broken.

Re: GURPS Magic - Creating gemstones
 

Yeah, it's mostly a patch on one of the more obvious ways creation spells mess with the concept of "valuable", but there is an important secondary issue in GURPS in that the high cost of large gems is one of the important limits on the proliferation of large Powerstones, which break a different economy and hence have several other kinds of strange seeming limits.

The fact that magic treats the value of gemstones as something special with respect to Powerstones actually helps to justify it treating it as something special with respect to Earth spells too.

Re: GURPS Magic - Creating gemstones
 

Either that or those things lose their value if compared to Earth, depending on the prevalence of Earth Magic.

That made me think of a setting where Earth Mages are powerful oligarchs who basically control the price and supply of every basic (elemental) metal.

Re: GURPS Magic - Creating gemstones
 

Not really. If a mage can make a 13-million carat (1 cubic yard) diamond for 3 energy, well, that makes diamonds cheap, but cheap diamonds don't have a lot of uses. There are minimal-at-best secondary effects, and the economy as a whole moves along just fine. It's largely a cosmetic matter.

This was important, but isn't in 4th edition.

Sure, when Powerstones had to be gemstones and were limited in capacity by their number of carats, not their price, stopping mages from waving a hand to make incredibly huge gemstones would limit Powerstones some (the 2-energy-cost casting of Earth to Stone in 3e was for an object up to 20 lbs, or a bit over 45,000 carats; the 5 energy cost version was for an object up to a hex in size, which, at the density of diamond, is over 23 million carats).

Now that it isn't true (4th edition does not restrict Powerstone materials, and simply varies the cost of enchantment based on the price of the underlying material), the gemstone restriction is largely vestigial. At best, it helps keep gemstones valuable enough that they make allowed subjects for the lower casting cost for Powerstone.

Re: GURPS Magic - Creating gemstones
 

It didn't even matter much back then. The main limiter of Powerstone size was (and really in 4e still is) the cumulative chance of the stone-shattering crit fail (and of course the 1 hour per pt investment of time in Q&D Enchantment rituals).

The old "Complete Powerstone" article figured that you'd go through 2 and 1/2 stones getting to 50 and 6 and 1/2 getting to 100. That breaks down to 6 days and 2 hours for the 50 pt stone and 12 days and 4 hours for the 100 pt one.

This of course assumes that all energy spent on Enchanting was regained from cheap Powerstones and with even just 1 pt stones you need 160 of them (which you store 6 feet apart) to fuel the daily Powerstone Enchantment.

Perhaps you consider 50 pt stones game-breaking but you'd still need 50 of those so you could have one to use every day (and of course 400 to fuel 50 pt Q&D rituals 8 times per day).

Even in the old days Powerstone abuse was limited by more than stone cost and 4e changed that less than may have been thought.

Re: GURPS Magic - Creating gemstones
 

Ah, but another issue isn't just that 3e Powerstone was limited by stone cost, but by gemstone supply. They're related, since limited supply tends to drive up price, but they aren't the same thing.

After all, the 3e rule wasn't about cost. The "$10×P² + $40×P" cost was just one of several assumptions about a given setting in the sidebar on p.22 of Magic (2nd edition), just like the daily pay for an enchanter. If a GM adopted a different cost for his setting (even ones as radically different as "a gemstone costs a flat $100 regardless of size" or "the price of a gem is $2^P, where P is the size in carats"), that didn't even rise to the level of a house rule, it was just a different setting assumption.

Rather, the actual rule, in the spell, was about gemstone size, 1 carat per point. Which means, if there are no gemstones of X carats available to the enchanter in a given setting, then it doesn't matter what the enchanter's budget is, he can't even try to make a X-point Powerstone. If the largest gemstone in the world masses 90 carats, a 100-point Powerstone is not expensive or difficult to make; it is an impossibility.

So, under the pre-4e rule, if Earth to Stone could have made gemstone, it wouldn't just fairly reliably save an enchanter money; it could also give him the ability to (attempt to) make something he otherwise couldn't make at all.

On the other hand, under 4e, the limit on Earth to Stone making gemstone is entirely irrelevant to the Powerstone maker, who doesn't have any intrinsic reason to care about gem availability at all.

Re: GURPS Magic - Creating gemstones
 

It would be a pretty trivial fix to say that for metaphysical reasons created gems can't be made into powerstones.

Re: GURPS Magic - Creating gemstones
 

Sure. The other reason on the limit is the previous, basically-cosmetic "We don't want use of diamond wine decanters to be almost as trivial as use of earthenware jugs, we want gems to be valuable treasure." It's just that prior to 4e, you got both the cosmetic and the Powerstone control with the same limit in the same Earth to Stone spell.

Re: GURPS Magic - Creating gemstones
 

Personally, I consider a “simple metal” to be either a pure metal or two component alloy. Carbon steel, yes. Bronze, yes. Admiralty brass (copper, zinc, tin), no. Doc Smith’s chrome-nickel-vanadium-molybdenum-tungsten carbon steel, what he called super-steel? You’ve got to be kidding me. And precious metals? Why not? The worst that’s likely to happen, in terms of legal problems, is agents of the Royal Mint either taking it and giving you a percentage, or asking (or insisting) that you stop. Honestly, by the time you’ve made enough to be asked to stop, you already more than enough for any reasonable purpose. Now, illegal problems are another matter entirely.