These are for raw, uncut gems. An uncut 5 carat diamond would have a base of 500 SP. Cutting gems increases their value although it reduces their weight, depending on the depth and nature of the cut. The cutting process includes polishing to enhance the value and appearance, and depends on the skill of the gemsmith. You could rule that a cut gem is up to half a carat less in weight, but retains the value. So that cut 5 carat diamond is actually 4.5 carats but is still worth 500 SP.
Obviously the base price will be lower in areas where such gems are more readily available, and higher in areas where they're not. But the above gives a good starting point.
mwsasser said Jan 13, 2013 16:20:02
That is good enough for me. I can tweak as needed. :-)
mwsasser said Jan 14, 2013 15:31:18
I've done some more reading on gems in the real world, it can be pretty complicated. There are different standards organizations for different stones in various countries that make it even worse. Value of the stone of course increases per rarity of the stone and that value is not linear the more rare it is.
But since we're talking diamonds as our example I'll stick with them. Cutting a stone typically adds 50% to its base value but the value of the stone is more than just carats. It's also the weight of the stone as well. As one gem website suggests, a 1 carat stone could be $1,000 but a 2 carat could be $4,000 based on weight and other factors. Rubies and sapphires seem to follow the same formula.
Cheaper stones can be very pretty but also quite cheap. 10 carat fire opals, while they are pretty, can be be as little as $30 but because they are so common.
So I suppose your post is an excellent starting point but it needs a bit of tweaking. :-) Hope others find this to be useful.
A simple way to emulate the increased value of the gems based on their weight could be to use the base values given by Loz and the multiply the value with the weight again. the formula would be:
Where X is the carats of them gem and y is the base value for that specific type of gem
So a diamond would be worth:
Now the only thing I know about diamonds is that girls like them, so I have no idea if these numbers are realistic for our world or not. But it is a simple way to make big and rare stones worth alot more than several small ones.
They really should ad that red wiggly line when I write my math down wrong!
thomas5251212 said Feb 03, 2013 09:06:06
As noted, there are tricky things to gemstone value (emeralds are proportionately more valuable than diamonds in the modern world both because there's much less of a stock of them, and because cutting diamonds is literally a science now but lapidary cutting is still largely an art) but that table Lawrence gave will work fine for an ancient or medieval world.