What is the size of an Onyx gem based on its worth.

[DoubleF]

Context: We are playing pathfinder and I am a Necromancer. I am trying to figure out how large is a 300 gp onyx? There was some discussion in the group regarding this, using a few methods of gold -> dollar conversion, since the size of gems is never discussed in the book, place onyx, using current prices and a 1:300 conversion rate at 3600 lbs, at a price of $0.06/gram. If we use a much more tame 1:100 conversion rate, it is still 1200 lbs. Some people have said that a gem should be approximately 20mm in diameter. This is roughly equivalent to what a $5 onyx would be today, which seems rather different. Obviously we could argue differences in mining capabilities, but would that truly make a difference of three levels of magnitude?.

[Satinavian]

Context: We are playing pathfinder and I am a Necromancer. I am trying to figure out how large is a 300 gp onyx? There was some discussion in the group regarding this, using a few methods of gold -> dollar conversion, since the size of gems is never discussed in the book, place onyx, using current prices and a 1:300 conversion rate at 3600 lbs, at a price of $0.06/gram. If we use a much more tame 1:100 conversion rate, it is still 1200 lbs. Some people have said that a gem should be approximately 20mm in diameter. This is roughly equivalent to what a $5 onyx would be today, which seems rather different. Obviously we could argue differences in mining capabilities, but would that truly make a difference of three levels of magnitude?.Maybe Onyx is rare after millenias of necromancy ?

I thing the authors just wanted a valuable component and went for a sufficiantly black gem without considering its price tag or how often it can be found in the real world.


Not that D&D pricelists make any sense or can be used for economic simulation otherwise. There is a reason they wrote stupid stuff like "those prices are what happens after adventurers and returned buried riches have completely upset the local economy" into earlier editions.

[Pauly]

Generally speaking with gems is that their prices increase exponentially.

A 2 carat diamong is not twice the price of 2 one carat diamonds becuase it is much rarer.

If a 1 carat gem is 1 GP Then a 2 carat gem would be t least 10 GP. A 3 carat 100 Gp, and so on.
So if you know the size of a standard stone for the standard price you can extrapolate from there. You don't have to use a factor of ten, maybe a factor of 20, maybe a fator of 5.

[Dappershire]

You also need to factor in that you, as a necromancer, need Spell-grade Onyx. Which is why wizards buy their ingredients from specialty stores, and not the nearest dwarf with a pick.
Also, using current pricing is complicated, given that the majority of black onyx sold on the market is artificially colored. This isn't a scam or merchant trick, most black onyx has been artificially colored for...I wanna say centuries. Yeah, centuries. Untreated black onyx exists, but is much rarer naturally.
300 gold worth, in one piece, would be a flat oval in the general dimensions of a woman's hand.

[Knaight]

...a price of $0.06/gram.

Where are you getting this figure? Putting aside how gemstones really don't get sold on a per gram basis except for the tiniest gemstones, this seems cheap even by the standards of tiny gems. A site (http://kamayojewelry.com/gemstones-names/chalcedony-stones/the-black-onyx-stone-of-powe) I looked at cited prices between $1/carat and $500/carat for onyx, which works out to $5/gram to $2500/gram - this is for gem grade onyx, others are well below. Using your price conversions, we're looking at between a $30,000 onyx or a $90,000 onyx. That could be as little as 36g, or as much as 6kg, but the 1200lb value doesn't show up here. Onyx has a density of 2.65 g/mL, so that light one is only 0.829 cubic inches. That's not huge, and for a single large gem that $500/carat figure is much more likely to be accurate than the $1/carat figure.

[Herobizkit]

Earlier editions also had different values based on whether they were cut or uncut gems.

From a quick Google search:

"Gems may occur naturally in several places, though most are found deep in underdark, subterranean settings, like mines. However, no matter where they are first found, they are always found in an unworked, uncut, raw, or rough condition. They may even look like simple rocks, and some might actually toss them around like they are valueless, never knowing their true nature or incredible value.

When properly cut and polished and worked, a gem's beauty is often likened to the work of the gods themselves, and their value - baring magic - is probably the highest in 'value to size' or 'value to weight' ratio. Thus, gems - and jewelry - are often used as a means to carry astonishing quantities of portable wealth."

Furthermore, smart merchants never pay full price/listed value for gems and the like if they can get away with it; similarly, they'd likely charge a hefty percentage to cut an unworked stone.

Finally, a blurb from the RPG StackExchange:

"Gems have 3 basic purposes in D&D.

*high-density currency; a chest of gems is much smaller than the same value of gold
*decoration, such as on jewelry or a ceremonial weapon
*money-sinks, restricting the availability of high-level spells."

Mechanically (ie. for Spell Component purposes), only the GP value available matters unless the spell calls for a specific TYPE and VALUE of Gem. QUALITY is assumed in the GP value.

[Coventry]

There is also the detail that Rich lampooned back in strip 667 (http://www.giantitp.com/comics/oots0677.html):

Apprentice: Master, I talked the shopkeeper down to only 400 gp for the rubies!
Master: Great, but the spell calls for 500 gp worth, so go back in and buy more.

That would lead to some very weird situations where the onyx buyer gets happier as the price-gouging goes up.

In short, the D&D economy is weird.

[Thrawn4]

The worth or price of an item is a result of offer and demand. It can be anything if you can come up with reasons as to why something is or is not available or desireable.

[Mastikator]

This is several layers of abstraction, some of which are based on subjective evaluation and supply and demand. There is no connection between the spell description and the actual size and purity of the onyx stone. It's impossible to infer. Your DM will have to make something up from scratch. The D&D/pathfinder economy is strictly limited to adventurers dungeon crawling and finding loot, it's not applicable to anything else and if you try you're gonna have a bad time. (which is why the system falls apart the moment the PCs become something else other than adventurers)

[erikun]

Obviously we could argue differences in mining capabilities, but would that truly make a difference of three levels of magnitude?.
Availability.

I really have no idea about the historical availability of onyx, but I'd rather expect that it was somewhat limited in ancient times. If it is like most gemstones, advances in mining and the global market have greatly helped to reduce the price, making them much easier to find and distribute. (This is what happened with amethyst, at least: large deposits in Brazil greatly reduced its value.) By contrast, gold is rare due to the small amounts of gold available in the world, and so the price stayed high and continues to rise due to limited availability.

I would not be looking at today's market value between gold and onyx as an assumption of how a medieval-like world would value the two materials, especially if one of them is constantly being consumed. Onyx is going to be in limited supply, and so you could probably value it at the rate the game books value other gemstones in general.

[Segev]

A couple of points:

"A 25 gp onyx" is not, as people have noted, a real measure in anything but game terms, because market prices are what people will pay for them. D&D gives gp values of gems because it's easier than trying to list carats and prices/carat. D&D has the simplistic assumption that the market value for the size and quality of gem you need is 25 gp per hit die (or whatever it is for other spells).

Additionally, we can infer from the description of the spell how big the onyx is. You put it either in the eye or mouth of the corpse. It must therefore be no bigger than you could fit in those sockets. Given that HD of a skeleton/zombie scale almost universally positively with size, we can roughly measure 25 gp worth of onyx by the number of HD creatures of various sizes have as skeletons and zombies.


Finally, as a third point, craft (gemcutting) can let you transform any starting gem into a gem 3x its value in gp, if you want to go with the spell literally requiring a "gp cost," or want to tie quality of cut to gp cost as well. Say, a better quality cut gem more perfectly channels the energies of the magic so you need less gem.

[sktarq]

Also gem prices today are not necessarily transferable to other eras at all.

Look at Amethyst for example. Today it is semi-precious stone, even is listed as such in some of the older D&D books. But back in Ye Olde Times it was a cardinal stone along with Rubies, Sapphires, Diamonds, and Emeralds. The Byzantine Empire really had a thing for them and they came from the Urals (and Ural or Russian type stones are still a much darker and intense purple that command a premium in today's market). But after the paler but enormous Brazilian loads were discovered the price fell through the floor (and more sources have been discovered since). So a 1000 gp amethyst would have changed radically in size across say the life span of gnome living in Europe.

So the question for your DM is has equivalent things happened to the onyx market in his world?

Also seconding the exponential growth issue about gem size to cost thing. Do a quick search of diamond cost at 1/4, 1/2, 1, and 2 carats to see what I mean and, if you wish, develop an equation you can use.