D&D 5e/Next WIP: Gem Size - Based on coins [Archive]

View Full Version : D&D 5e/Next WIP: Gem Size - Based on coins

Zhorn

2020-04-28, 10:39 AM

So in one of the 5e threads recently, someone asked about gem sizes in 5e since the DMG doesn't give much info on the subject.
Individually, gems are treated as small and light, and as long as you don't carry many on you they are considered to be inconsequential.
But say you wanted to deal in gem sizes. What's the difference between a 50 gp diamond and a 5,000 gp diamond? How about a 500 gp moonstone vs 500 gp emerald?

I've been toying around with this idea for a while now, and after that question was asked in the forums I've decided to have another look at it, and share where my brain is headed so far.

First up, since the are compared to coins, their size and weight in relation to coins seems like a good measurement to go by.
So how big is a coin?

While we can math out a volume of 1lb. of D&D gold from the 5 lb. gold trade bar (DMG p20), anyone who's done the math on that will tell you you'll end up with some pitifully thin coins if you want to use the standard 1 inch diameter (0.025 inch thick). And if you go by the density of real world gold it's even worse (0.018 inch thick).

Scrap those two ideas, and go old school.
3.5e Draconomicon gave a coin size of 1 inch diameter with a 0.1 inch thickness. That's much more coin-like. gives us a volume of 0.078539816 cubic inches per coin (there's rounding off later, don't panic).

Now we can work out a range of sizes and express them as a equivalent number of coins, or as a sphere's diameter (gems can be also any shape, sphere's are just nice and uniform and easier to imagine)

Next is assigning values. I went with using the gem values in the DMG as the '100 coins in size' value for a few reasons.
Spits out a volume similar to 1 lb. of real world diamonds (I'll be futzing with the weight later, but this was just nice)
Gives the the lowest possible price of the smallest stone size I set to the cheapest gemstone type still within the currency system
2.5 inches is a nice visual image for a fantasy gem
Conveniently aligns the value of SKT's 'grapefruit sized pearls' in the grapefruit size range (4 to 6 inches, lands nicely on 5)
Plugging these values into excel, tweaking the number of coin denominations to get close to an idea diameter
(Coin Volume * Number of coins, then back calculate a radius for a sphere of that size.)

Volume (cubic inches)
0.007853982
0.078539816
0.392699082
3.926990817
7.853981634
15.70796327
39.26990817
78.53981634

Diameter (inches)
0.246621207
0.531329285
0.908560296
1.957433821
2.466212074
3.107232506
4.217163327
5.313292846

Rounded Diameter
0.25
0.5
1
2
2.5
3
4
5

Coins in Size
0.1
1
5
50
100
200
500
1000

Modifier
Description / Size
Diminutive / Fine
Tiny
Very Small
Small
Average
Large
Very Large
Huge

10 gp
Ornate Stone
0.01 gp = 1 cp
0.1 gp = 1 sp
0.5 gp = 5 sp
5 gp
10 gp
20 gp
50 gp
100 gp

50 gp
Semi-precious Stones
0.05 gp = 5 cp
0.5 gp = 5 sp
2.5 gp = 25 sp
25 gp
50 gp
100 gp
250 gp
500 gp

100 gp
Fancy Stones
0.1 gp = 1 sp
1 gp
5 gp
50 gp
100 gp
200 gp
500 gp
1,000 gp

500 gp
Fancy Stones (Precious)
0.5 gp = 5 sp
5 gp
25 gp
250 gp
500 gp
1,000 gp
2,500 gp
5,000 gp

1,000 gp
Gem Stones
1 gp
10 gp
50 gp
500 gp
1,000 gp
2,000 gp
5,000 gp
10,000 gp

5,000 gp
Gem Stones (Jewels)
5 gp
50 gp
250 gp
2,500 gp
5,000 gp
10,000 gp
25,000 gp
50,000 gp

Calculation method can also be extended to work out further sizes (didn't want to get too carried away).
Say you wanted to know just how big a 1000 gp agate would be compared to it's 2.5 inch/10 gp counterpart? Roughly 11.5 inch diameter. That's one hefty stone needed for Awaken, might want to look into a more precious form of agate to get a smaller gem.

So now we have Sizes, and we have values. Final step: weight.

I'm of two minds about this:

Method 1: By the book. SKT p206 gives us a Coral value-to-weight of 1 lb. = 100 gp. Since coral is a 100 gp gemstone and our average size is set at 100 coins: Set gems at a weight to volume of 100 coins in gems = 1 lb.

Method 2: the lb/in3 difference of real world diamond compared to gold is roughly 1/5th, so with 50 gold coins to 1 lb, then the volume of 250 coins in gems = 1 lb.

so yeah, that's what I have so far.
Thoughts? Inputs? Recommendations? Adjustments?

hamishspence

2020-04-28, 10:59 AM

IMO the best way to justify "Draconomicon coins" is to say that they are mostly empty space - more like bicycle wheels than regular coins - rim and spokes, to give them rigidity, but next to no metal in between spokes.

As to gems - I'd favour erring on the small size - so that they're portable wealth, more so than platinum coins would be.

Segev

2020-04-28, 11:16 AM

IMO the best way to justify "Draconomicon coins" is to say that they are mostly empty space - more like bicycle wheels than regular coins - rim and spokes, to give them rigidity, but next to no metal in between spokes.

As to gems - I'd favour erring on the small size - so that they're portable wealth, more so than platinum coins would be.

The best visual I've heard for something approaching having gold pieces in D&D resemble reasonable weight and value and volume is to think of them as bieng sized like dimes. An American dime is .7 inches in diameter, and .05 inches thick. That's .035 cubic inches. It's fairly rigid, but admittedly isn't gold. Still, a gold coin of that size is likely not so soft that you would see it bending and getting crushed just from casual use and storage.

A dime-sized gold coin would weigh .024 lbs. 50 of them would be 1.2 lbs, which is just about right (technically, 41 coins would be 1 lb). Make the coins the thickness of a dime but only just over half an inch (.56) in diameter, and you hit it right on the nose for weight.

Zhorn

2020-04-29, 12:06 AM

IMO the best way to justify "Draconomicon coins" is to say that they are mostly empty space - more like bicycle wheels than regular coins - rim and spokes, to give them rigidity, but next to no metal in between spokes.

Non-standard shapes are a fun concept visually, and there are penty of coin designs out there that use negative space as part of coin design. But as a common concept, the majority of coin depictions in real life and fantasy is the classic solid disc. It's simple and lets everyone have the same mental image without the need of a complex physical representation (though some of those etsy sets are just gorgeous).

There's also the benefit of if I use the Draconomicon coin sizes , I can just use the values they give for cois and loose stacks for containers to work out phisical hoard and cache sizes. Plus, a measurement from official source material (even if from an older edition) gives a common reference point. Don't need to invent as 'new standard' when an old standard suits the purpose needed.

As to gems - I'd favour erring on the small size - so that they're portable wealth, more so than platinum coins would be.

Which this does do for the most part, just with the wide disparity in gem values (10 to 5,000), different stone are going to come into play as being better than different coinage.
Based on the values in my original post:
Ornate Stones (10 gp) have more value per size than copper pieces (10:1)
Semi-Precious Stones (50 gp) have more value per size than silver pieces (5:1)
Fancy Stones (100 gp) have more value per size than electrum pieces (2:1), and are on par with gold pieces (1:1)
Fancy Stones (Precious) (500 gp) have more value per size than gold pieces (5:1)
Gem Stones (1,000 gp) are on par with platinum pieces (1:1)
Gem Stones (Jewels) (5,000 gp) have more value per size than platinum pieces (5:1)

If I set the scale at Ornate Stones (10 gp) being more valuable than platinum pieces, let's say 2:1, then a 50 gp diamond would be barely 0.2 inch in dimeter, which is rediculously small and undercuts the whole fantasy trope of larger gems (compared to 50 gp diamond = 1 coin in size).
Ruby of the War Mage being a 1 inch gem (XGtE, p138) ends up being a common magic item with a material value of +5,000 gp, which is a bit much.

You want to hit a balance point in value to size where you can have a scattering of gems in a pile having a visible presence, while not being so overwhelmingly more valuable as to negate the worth of the remaining treasure.

The best visual I've heard for something approaching having gold pieces in D&D resemble reasonable weight and value and volume is to think of them as bieng sized like dimes. An American dime is .7 inches in diameter, and .05 inches thick. That's .035 cubic inches. It's fairly rigid, but admittedly isn't gold. Still, a gold coin of that size is likely not so soft that you would see it bending and getting crushed just from casual use and storage.

A dime-sized gold coin would weigh .024 lbs. 50 of them would be 1.2 lbs, which is just about right (technically, 41 coins would be 1 lb). Make the coins the thickness of a dime but only just over half an inch (.56) in diameter, and you hit it right on the nose for weight.

Which while I do like the idea behind trying to scale coins to real gold, the coins just feel too small at that scale (in Australia, our five-cent is a close comparison to the US dime, so I have a physical prop to compare to).

Then there's also the system consistency. Do you have different sized coinage for silver, copper, electrum, and platinum also?
Viable, but a nightmare for calculations (going back to the Draconomicon, it already gives sized and volumes for piles and containers of loosely stacked coins). A big part of what makes that work is all coins are the same size regardless of what metal they are made of. A coin as a standard unit of size, which doubles back into what this system is aiming for. And if all coins are going to be ther same size, most of them will be wrong in terms of weight:volume compared to their real world counterparts anyway, so why add all the extra work? (we're also not looking at different weights for each type of gem, just a single one to cover all of them)

Now like with the gem size, having a common size too small just feels off. If you can get your hands on an Australia one dollar coin, compare that to a dime. The Austalian one dollar is a very close example of what a Draconomicon dimensioned coin would be and will give you a good sense of size.

But still, to give the dime measurement a fair go, lets take that as out standard coin size and aim to hit the same gp values to see what the sizes look like and what distibution of coins is needed.
Diameter: 0.75 , Thickness: 0.05 , Volume: 0.022089323

Where my original I set 100 coins because it gave me a starting point close to 2.5 inch diameter (plus other reasons), so I'll do the same here.

Volume (cubic inches)
0.002208932
0.022089323
0.110446617
1.104466167
2.208932335
4.417864669
11.04466167
22.08932335

Diameter (inches)
0.161582602
0.348119163
0.595275394
1.28248196
1.615826018
2.035813212
2.763023624
3.481191625

Coins in Size
0.1
1
5
50
100
200
500
1000

Modifier
Description / Size
Diminutive / Fine
Tiny
Very Small
Small
Average
Large
Very Large
Huge

10 gp
Ornate Stone
0.01 gp
0.1 gp
0.5 gp
5 gp
10 gp
20 gp
50 gp
100 gp

50 gp
Semi-precious Stones
0.05 gp
0.5 gp
2.5 gp
25 gp
50 gp
100 gp
250 gp
500 gp

100 gp
Fancy Stones
0.1 gp
1 gp
5 gp
50 gp
100 gp
200 gp
500 gp
1000 gp

500 gp
Fancy Stones (Precious)
0.5 gp
5 gp
25 gp
250 gp
500 gp
1000 gp
2500 gp
5000 gp

1000 gp
Gem Stones
1 gp
10 gp
50 gp
500 gp
1000 gp
2000 gp
5000 gp
10000 gp

5000 gp
Gem Stones (Jewels)
5 gp
50 gp
250 gp
2500 gp
5000 gp
10000 gp
25000 gp
50000 gp

Now since there is less total volume to work with, we can try and alternate average of 80 coins as it would give a spot on diameter of 1.5 inches without rounding.

Volume (cubic inches)
0.001767146
0.017671459
0.088357293
0.883572934
1.767145868
3.534291735
8.835729338
17.67145868

Diameter (inches)
0.15
0.323165204
0.552604725
1.190550789
1.5
1.889881575
2.56496392
3.231652035

Coins in Size
0.08
0.8
4
40
80
160
400
800

Modifier
Description / Size
Diminutive / Fine
Tiny
Very Small
Small
Average
Large
Very Large
Huge

10 gp
Ornate Stone
0.01 gp
0.1 gp
0.5 gp
5 gp
10 gp
20 gp
50 gp
100 gp

50 gp
Semi-precious Stones
0.05 gp
0.5 gp
2.5 gp
25 gp
50 gp
100 gp
250 gp
500 gp

100 gp
Fancy Stones
0.1 gp
1 gp
5 gp
50 gp
100 gp
200 gp
500 gp
1000 gp

500 gp
Fancy Stones (Precious)
0.5 gp
5 gp
25 gp
250 gp
500 gp
1000 gp
2500 gp
5000 gp

1000 gp
Gem Stones
1 gp
10 gp
50 gp
500 gp
1000 gp
2000 gp
5000 gp
10000 gp

5000 gp
Gem Stones (Jewels)
5 gp
50 gp
250 gp
2500 gp
5000 gp
10000 gp
25000 gp
50000 gp

Make of the rounding as you will, but so far I still have a preference for the size progression in my original post.

Breccia

2020-04-29, 01:22 PM

Some real-life info if it helps.

A real-life dime is 8.33% nickel plate over copper. It has a mass of 2.268 grams. If it was solid gold, it would have a mass of 4.912 grams and, as of noon today, would have gold value of $270 dollars, give or take bus fare. Incidentally, the price for gold is about the same as it was June 2013, that'll be important later.

https://i.pinimg.com/originals/9c/dd/5b/9cdd5b579e08d42377c2d52a75009e70.jpg

https://d1syye9ivgdomp.cloudfront.net/wp-content/uploads/2017/11/main-qimg-b789c55feec6052c01783508af81b496-c-1.jpg

Even the "large" 4.0 carat gem, that's 0.8 grams, is pretty small, even compared to the smallest US coin.

Thing is, gem values skyrocket by size. Gold scales linearly, because you can just cut it up into pieces. Gemstones do not, as larger size gems of good quality/color are harder to find. The Rapaport price guide, which I'm using without anything better onhand and happen to have a 2013 copy from earlier D&D work, says that a good color, good quality 1-carat diamond would be about $9,000. A quick stroll around various sites gave a wide spread of values, but $9,000 seemed to fit that spread.

However, the price guide says the same color, same quality, 2.0 carat diamond would be $34,600.

Three carats, $89,100

And four carats, a whopping $157,000 -- which in turn is 17 of the 1.0-carat gems and 581 of those gold coins at one-three-thousand-five-hundreth the weight.

While the diamond-gold conversion doesn't match D&D fantasy rules, the scaling of gemstone value is what I really wanted to get out there. It's almost a squared relationship.

Hopefully you find something in there that helps.

Segev

2020-04-29, 01:48 PM

Ah, shoot, relooking at my numbers, I am pretty sure I was using the wrong formula for volume of a cylinder. I think I was getting excited about being able to use the diameter instead of the radius, so accidentally mentally did pi*d (circumference) rather than pi*(d/2)2 (area). So my numbers in my earlier post are off, and I don't have the time to fix them right now. It'll probably take a whole extra post. Sorry about that.

JNAProductions

2020-04-29, 08:27 PM

Google says (https://www.google.com/search?q=volume+of+a+dime&oq=volume+of+a+dime&aqs=chrome..69i57j0l7.4190j0j7&sourceid=chrome&ie=UTF-8) .02 cubic inches.

Wolfram Alpha (https://www.wolframalpha.com/) (awesome site!) says (https://www.wolframalpha.com/input/?i=.02+cubic+inches+of+gold) that is 6.33 grams of gold.

It further says (https://www.wolframalpha.com/input/?i=6.33+grams) that 6.33 grams is .2233 oz.

So that's 71.65 dime-sized coins to the pound.

Zhorn

2020-04-29, 11:47 PM

...carat...

I've seen a lot of posts in the past about trying to incorporate carats into the size calculation (most of them just half formed ideas expressed as a concept rather than a complete system), and was even looking at attempting it myself at one point.
Problem being that the value scale just shoots up too fast in real world values of carats to volume, and the amount of carats in a pounds is also incredibly high.
Possible if you want all gems to only be on the tiny scale as with that ring picture.

but if you like to picture treasure as the Treasure Planet example
https://i.pinimg.com/originals/ef/29/f1/ef29f1d50020be11e089a6571ee41f06.jpg
then your average gem will need to be larger than jewellery stones, and you'll need to value them accordingly so that other treasure still retains notable value in comparison (lesser, but not insignificant).

Now with that carat:size:value system of real world diamonds roughly following a squared relationship, scaling gems up or down if size just gets too complex that you'll need to use a complicated formula every time.

Hence dropping all that in favour of a simple linear relationship.
Say gem X is worth 5,000
If want a value of 500, then you want a gem 1/10th the volume.
If want a value of 10,000, then you want a gem x2 the volume.

Simple enough to not need a calculator, which for the table is a big plus.
If you can think of a simple method that uses carats, I'll be all ears for that, but I doubt it'll be easy to find.

Ah, shoot, relooking at my numbers, I am pretty sure I was using the wrong formula for volume of a cylinder. I think I was getting excited about being able to use the diameter instead of the radius, so accidentally mentally did pi*d (circumference) rather than pi*(d/2)2 (area). So my numbers in my earlier post are off, and I don't have the time to fix them right now. It'll probably take a whole extra post. Sorry about that.

All good, you still gave the other dimensions, which were what I use in my spreadsheet anyway.

Getting a 'perfect' coin just won't work if trying for real world metal densities.

Just use simplified fantasy materials.

Books give us coins weights ~1/3rd of an ounce (0.32 oz.), 50 coins to a pound (0.02 lb. each). This is pretty constant across multiple editions.
3.5 Draconomic gives a uniform coin size. does it align with any of the real world metal weights? Hah, no.
copper coin: 0.41 oz.
silver coin: 0.48 oz.
gold coin: 0.88 oz.
platinum coin: 0.98 oz.
None of it matches. The value were chosen for the convenience of a mechanics relation.
And for a game, that fine. Simplified values is good. All metals are unobtainium as needed (Or made with a whole lot of internal negative space to match hamishspence's justification).

Now one you decide to measure things by a standardised coin size, that coin could be any size and the system still works (as demonstrated with plugging in the dime values).
From there it's just a matter of picking a size range for your coin size and what size gem you configure to.
I like meatier coins than dimes, and gems having that fantasy 'chunkiness' to them because of how those values line up to the things valued and sized in the modules (ie; it aligns to the fantasy).

Now the diameter aspect is something I just use as a frame of reference, but will unlikely use in my games unless something already uses the measurement (such as the giants pearls in SKT, or the Ruby of the War Mage in XGtE).
Most gems are not going to be perfectly spherical, and will be odd shaped to each other, so going for odd diameter sizes would be fine so long as your other scaling is kept in multipliers of 2's, 5's and 10's for simple at-the-table calculation.

How big is this gem X? Gem X is 5 coins in size
How many can I fit in this chest? 1/5th as many coins that you'd fit in there.
What if it's a mix of gems and coins? Count your gems by their coin sizes, combine with the coins, calculate as if it were just coins.

Pyotrnator

2020-04-30, 12:09 AM

hamishspence

2020-04-30, 12:38 AM

And for a game, that fine. Simplified values is good. All metals are unobtainium as needed (Or made with a whole lot of internal negative space to match hamishspence's justification).

Technically the negative space can be external rather than internal, but such a coin would be rather weird looking - thick rim, thick spot in the center, bracing struts, and in between the bracing struts, incredibly thin metal more like foil. Basically looking more like a bicycle wheel than a coin.

That's the only way to make Draconomicon coin sizes conform with D&D coin masses, and not have hollow coins.

Zhorn

2020-04-30, 01:24 AM

Technically the negative space can be external rather than internal, but such a coin would be rather weird looking - thick rim, thick spot in the center, bracing struts, and in between the bracing struts, incredibly thin metal more like foil. Basically looking more like a bicycle wheel than a coin.

That's the only way to make Draconomicon coin sizes conform with D&D coin masses, and not have hollow coins.

Right, sorry. I meant internal as 'inside the bounding shape' of the coin. Communication error.

You get a pretty good fit to the data provided by Breccia here using the following formula*:

Cost = 104 * m2

m is mass in carats.

As such, I'd recommend scaling with the square of the volume (or mass) of the gem. (EDIT: I missed that Breccia also noted that "it's almost a squared relationship". Regardless, I was surprised at how neatly it came out. It's rare that I do a regression and see coefficients so close to integer values)

*exponentiation factors rounded to the nearest integer for simplicity (don't worry - each factor was only changed by a few percent at most).
Sorry, I don't quite follow this, could you post some calculations to express what you mean?
I tried applying this but it looks like it was only meant for a single gemstone type

Ornate Stone
Semi-precious Stones
Fancy Stones
Fancy Stones (Precious)
Gem Stones
Gem Stones (Jewels)

Cost = 104 * m2
10 gp
50 gp
100 gp
500 gp
1000 gp
5000 gp

m = (Cost / 104)1/2
0.1
0.223606798
0.316227766
0.707106781
1
2.236067977

rounded (0.00)
0.10
0.22
0.32
0.71
1.00
2.24

not seeing how this can be used as is

Segev

2020-04-30, 10:41 AM

Yeah, I considered whether a coin could be like the old Chinese ones, with holes in the middle, but just using .88 oz as the weight of a "full" gold coin of Draconomicon size, vs. .32 oz of a "1/50 lb. weight" gold coin... to make a Draconomicon-sized coin that is the stated weight would mean we have only about 36% of the coin in annulus. i.e. the hole in the middle must encompass 64% of the coin.

If it's a circular hole, 64% of a half-inch-radius circle is .4 inches (radius). So that means you've got a tenth of an inch in "rim thickness" of the annulus. That's just intractable. That's an oversized ring, not a coin.

Zhorn

2020-04-30, 10:59 AM

Aiming for realism is all well and good, but when it's adding complexity upon complexity for no real gain, sometimes it's better to just step back and say "is this actually adding any value at all, or even helping achieve what I want to achieve in a fantasy game about mythical monsters and magic?"

The whole basis of this system it to strip back gem sizing into an easy to measure metric.
Basing coins on real world gold (which the game has never done well in the first place) means a lot of the pre-existing numbers won't be usable. Do I gain anything from reinventing that wheel, or do those old numbers serve what I need?
Short answer: use what's easiest and involves the least work.

Luck just has it that those old numbers also cause a nice lineup (or close enough to) on a handful of other things.

Pyotrnator

2020-04-30, 11:06 AM

Right, sorry. I meant internal as 'inside the bounding shape' of the coin. Communication error.

Sorry, I don't quite follow this, could you post some calculations to express what you mean?
I tried applying this but it looks like it was only meant for a single gemstone type

Ornate Stone
Semi-precious Stones
Fancy Stones
Fancy Stones (Precious)
Gem Stones
Gem Stones (Jewels)

Cost = 104 * m2
10 gp
50 gp
100 gp
500 gp
1000 gp
5000 gp

m = (Cost / 104)1/2
0.1
0.223606798
0.316227766
0.707106781
1
2.236067977

rounded (0.00)
0.10
0.22
0.32
0.71
1.00
2.24

not seeing how this can be used as is

Apologies for the lack of clarity. The particular formula I gave was in reference to price of diamonds per carat in dollars, using the real-world diamond cost data supplied by Breccia.

The important thing about the formula I gave is the square relationship. To use this, you need to select the price at one size for a given type of gem to set the price for all sizes for a given type of gem. (note that your "diminutive/fine" size amounts to about 2 carats when you're dealing with diamonds, if I did my conversions right).

As such, if you say that a gem of mass mo has value Vo, you'd calculate the value V of a gem of the same type with mass m using the formula:

V = Vo * (m/mo)2

(being sure to use the same units for m and mo)

As such, if you say that a 1 carat diamond is worth 100 gold, then a 10 carat (2 gram) diamond would be worth 100 * (10/1)2 = 10,000 gold.

Similarly, if you say that a 2 lb agate is worth 75 gold* and want to calculate the value of a 0.25 lb agate, the 0.25 lb agate would be worth 75 * (0.25/2)2 = 1.17 gold.

Hope this is more clear than my last post.

*I have no idea of how much agate sells for in the real world.

Zhorn

2020-04-30, 11:29 AM

Cheers for looking into it, but unfortunately that math is just getting too complex for the intended goal of this side project, and relies on tying to real world gemstone economies to derive weight-to-values which I'm not sure serves any benefit to the game.
Still, interesting work on your part.

Zhorn

2020-05-02, 06:02 AM

Things still bouncing about my head with this:

Considering moving the average to 50 coins in size. A 2 inch diameter is pretty decent. Or maybe keep with the 100 coin as average just for the convienient number alignments it yeilds?
Maybe drop the size smaller than 1 coin in size. 0.5 diameter is small enough, but not sure if I should rule out the 0.25 inch diameter just yet.
Introduce a 25 coin sized gem? I think that one maths out close to 1.5 inch diameter. would make it less of a jump from 5 directly to 50.
Is there a pattern that utilises 2's,5's,10's for multiplying the sizes that hold some consistency? I know if I switch to a cubic-volume relationship (ie: multiple the diameter by value X is multiplying the volume by the cube of value X) for the coin sizes it'll hold consistently, but the values of smaller/larger gems takes a sharp turn away from simple numbers using multiples of 5 times by some power of 10.
I like the weight relation of 1:5 when comparing gems to coins, it holds a close approximation to reality, but isn't tied to a specific value so it's simple to scale up or down with any changes in metal weights in game.

Knaight

2020-05-02, 10:42 AM

That's the only way to make Draconomicon coin sizes conform with D&D coin masses, and not have hollow coins.
Impure alloys could also work here, and pure gold isn't used for much at all in jewelry due to its softness.

Zhorn

2020-05-02, 11:08 AM

Impure alloys could also work here, and pure gold isn't used for much at all in jewelry due to its softness.
The PHB (p157) already establishes gold as a tradegood being 1 lb. = 50 gp, along with the other metals aligning their tradegood values with the 50 coins to a pound rule, so impure alloys would just lend itself to introducing more recalculating work in other areas if you want to do that and maintain those consistencies.

I'm actually perfectly fine with the weight of gold not being 100% accurate, same with all of the metals.
Different sized coinage for the purposes of the game is one of those needless complications, so I find it easier to just have them all the same size and weight.
I don't find it adds much at all to the game to split hairs over the realism of the weight differences between copper, silver, gold, platinum, electrum, mithral, adamantine, iron, etc.

50 pure copper coins taking up the same volume and weigh the same as 50 pure gold coins? Yep, not going to loose sleep over that. It's a minor detail that doesn't cause any problems.

But anyway, this thread was about gems sizing them using a standard coin size as a unit of measurement.

Nifft

2020-05-03, 01:44 PM

What I'm hearing in this thread is that Scrooge McDuck actually dives into a vault full of aluminum coins, each of which is merely gold-plated.

If you did that -- used a cheap metal for the base, then coated it with some quantity of the "face" metal -- then you might be able to justify all types of coins weighing the same.

Zhorn

2020-05-04, 02:47 AM

What I'm hearing in this thread is that Scrooge McDuck actually dives into a vault full of aluminum coins, each of which is merely gold-plated.
First off, how dare you disrespect the value integrity of Scrooge's money bin. That is 100% legitimate pure quality dosh right there!
Second, it wouldn't matter how light of dense the coins where in that trove, Scrooge would have eventually worked his way up to being able to swim in it.

https://www.youtube.com/watch?v=ux4i0_RIf3c
(Also, Scrooge is the best example of an adventurer, bar none)

If you did that -- used a cheap metal for the base, then coated it with some quantity of the "face" metal -- then you might be able to justify all types of coins weighing the same.
Finally, I'm not concerned about justifying the coin volume to weights at all. The 3.5 Draconomicon gave me a value that suits my needs and I'll use it.
The purpose of this thread (if we could steer back to the topic) in setting a value of gems in relation to coins, with a set standardised coin (provided) as the metric to measure by.

sandmote

2020-05-04, 02:20 PM

This is great.

Gold is among the densest metals, so I wouldn't use it as a standard for weight in comparison to gemstones. Sure, it's the default for d&d, but it'll still be odd to have gems compared to it. The comparison to coral from SKT is probably fine.

Otherwise, I'd maybe lay out a list of how you're counting each gem. Agate as an ornate stone sounds odd to me (I'd assume that category applies to anything that isn't even "semi-precious"), for instance. Maybe some examples could get an approximate per carat value for each category?

For use of this in spellcasting, I think the main thing missing is how to value volumes of gemstone dust.
Individual Gem:

Astral Projection: 1000 gp jacinth
Awaken: 1,000 gp agate
Chromatic Orb: 50 gp diamond
Circle of Death: 500 gp pearl (crushed)
Clone: 1000 gp diamond
Create Undead: 150 gp black onyx
Drawmij's Instant Summons: 1000 gp sapphire
Gate: 5000 gp diamond
Identify: 100 gp pearl
Infernal Calling: 999 gp ruby
Magic Jar: 500 gp, any type
Magnificent Mansion: 5 gp piece of marble
Mighty Fortress: 500 gp diamond
Raise Dead: 500 gp diamond
Resurrection: 1000 gp diamond
Planar Binding: 1000 gp, any jewel

other:/

Clairvoyance (hearing option): 100 jeweled horn
Contingency: 1500 gp ivory statuette decorated with gems
Create Homunculus: 1000 gp jewel encrusted dagger
hero's feast: 5000 gp gem encrusted bowl
Revivify: 300 gp diamonds (allows multiple)
shapechange: 1500 jade circlet
True Resurrection: 25000 diamond (allows multiple)

gemstone dust:

Continual Flame: 50 gp of ruby dust
Forbiddance: 1000 gp of ruby dust
Forcecage: 1500 gp of ruby dust
Glyph of Warding: 200 gp of diamond dust
Greater Restoration: 100 gp of diamond dust
magic mouth: 10 gp of jade dust
Nondetection: 25 gp of diamond dust
Programmed illusion: 25 gp of jade dust
Sequester: 1000 of diamond, emerald, ruby, and sapphire dust
Simulacrum: 1500 gp of ruby dust
Stoneskin: 100 gp of diamond dust

Cheap Stone (No Listed Price):

Darkvision: agate
Disintegrate: lodestone
Erupting Earth: obsidian
Leomund's Tiny Hut: crystal bead
Mending: two lodestones
Moonbeam: opalescent feldspar
Mordenkainen's Private Sanctum: chrysolite powder
Otiluke's Resilient Sphere: crystal sphere
Resilient Sphere: crystal hemisphere
Shatter: mica
Sunburst: sunstone
Wall of Force: crushed clear gem

Zhorn

2020-05-04, 10:21 PM

Gold is among the densest metals, so I wouldn't use it as a standard for weight in comparison to gemstones. Sure, it's the default for d&d, but it'll still be odd to have gems compared to it. The comparison to coral from SKT is probably fine.
In a general sense I agree with ignoring real world weights beyond as a conceptual frame of reference.
As hamishspence touched on in their first response, gems are supposed to be a more portable form of wealth. In the DMG it specifies
Gemstones. Gemstones are small, lightweight, and easily secured compared to their same value in coins.So from there we know whatever values we pick, we just need to make sure that those aspects are tilted in favour of gems.
Short version: Whatever the coins weigh, the same volume of gems weigh less.
Next is looking at what is convenient for the table. this usually means restricting math to simple multiples of 2 or 5 (by extension 10's also).

By 2's is nice because of that alignment to SKT coral, and gives a nice 100 to 1 lb., but undersells that lighter weight fact (still present, but only a 2:1) which is the big hesitating factor for me as it just doesn't feel significant enough, despite my usual preference of prioritising values from the book first. The flip side of this is if I were to use obsidian from the same book (SKT, p229); it has 4 inch diameter obsidian spheres weighing 25 lb. which would be heavier than real world gold. Also, on further reading there's another value for coral (SKT, p204) setting it as 50 gp per 1 lb., setting up the same value-to-wight as D&D gold... The more I read, the more unsure of using the book as a benchmark I get.

By 5's is a bigger emphasis on gems being lighter. While closer to reality, it is doing a big rounding off to get to a clean figure like that.
The comparison between diamonds to gold to get to here was just those are the two 'iconic' substances of their respective gem and metal family groups and was a close-ish ballpark figure to that 5:1 ratio. I could have compared the densities of any other gem (https://www.ajsgem.com/articles/gemstone-density-definitive-guide.html) to any other metal (https://www.engineersedge.com/materials/densities_of_metals_and_elements_table_13976.htm) and gotten wildly different results. This is a general trend when I use real world values in D&D, round off heavily to get to simple-to-work-with numbers.

Otherwise, I'd maybe lay out a list of how you're counting each gem. Agate as an ornate stone sounds odd to me (I'd assume that category applies to anything that isn't even "semi-precious"), for instance.
The name categories for each value of gem is a carryover from AD&D 1e's DMG p25 (unfortunately it didn't give details on sizes beyond just saying small, average, large etc), where the values aligned with the values given in 5e. It was just quicker to reuse those terms rather than write out every singe gem.
So Ornate Stones is every gem type in the '10 gp' category, Fancy Stones is everything in the '100 gp' category, etc
All listed forms of Agates are in the '10 gp' group, that's the only reason they would class as Ornate Stones.

Maybe some examples could get an approximate per carat value for each category?
Too much work for questionably any benefit. If anything trying to use carats will undermine the whole system's aim at simplicity.
Carats being a function of weight means if two gems have different carat values, they should have different weights.
It pretty much is setting up the same challenge as coins of different metals, where if you account for their respective densities then the coins have to be different sizes.
example: 1 cubic in of quartz (127.33 carat) vs diamond (287.92 carat). it's much simpler to work in the values that are already given in the books, and treat the other factors as being equal for the comparison (same as what I'm already doing for coins by using the 3.5e Draconomicon).
An equal volume of Quartz and Diamond, both weighing the same. Quartz is a 50gp stone, Diamond is a 5000gp stone.
Say we set out baseline at 100 coins in size, A quartz 10 coins in size is 5gp, a Diamond 10 coins in size is 500gp. Simple barebones math with no need for carats.

If you can come up with a method of using carats (I don't even know of any official sources that use carats in D&D), then I'll be happy to read it. But it needs to (1) serve a purpose, and (2) be reasonably simple to work with. But as far as it looks to me, it's adding in a bunch of values which will just complicate the equations, and don't serve any particular purpose.

With this table that I'm working on, once the values are locked in, the formulas are going to be stripped away so it's just a handful of sizes in coin allotments and a few diameter sizes listed for a frame of reference.

For use of this in spellcasting, I think the main thing missing is how to value volumes of gemstone dust.
Individual Gem:

Astral Projection: 1000 gp jacinth
Awaken: 1,000 gp agate
Chromatic Orb: 50 gp diamond
Circle of Death: 500 gp pearl (crushed)
Clone: 1000 gp diamond
Create Undead: 150 gp black onyx
Drawmij's Instant Summons: 1000 gp sapphire
Gate: 5000 gp diamond
Identify: 100 gp pearl
Infernal Calling: 999 gp ruby
Magic Jar: 500 gp, any type
Magnificent Mansion: 5 gp piece of marble
Mighty Fortress: 500 gp diamond
Raise Dead: 500 gp diamond
Resurrection: 1000 gp diamond
Planar Binding: 1000 gp, any jewel

other:/

Clairvoyance (hearing option): 100 jeweled horn
Contingency: 1500 gp ivory statuette decorated with gems
Create Homunculus: 1000 gp jewel encrusted dagger
hero's feast: 5000 gp gem encrusted bowl
Revivify: 300 gp diamonds (allows multiple)
shapechange: 1500 jade circlet
True Resurrection: 25000 diamond (allows multiple)

gemstone dust:

Continual Flame: 50 gp of ruby dust
Forbiddance: 1000 gp of ruby dust
Forcecage: 1500 gp of ruby dust
Glyph of Warding: 200 gp of diamond dust
Greater Restoration: 100 gp of diamond dust
magic mouth: 10 gp of jade dust
Nondetection: 25 gp of diamond dust
Programmed illusion: 25 gp of jade dust
Sequester: 1000 of diamond, emerald, ruby, and sapphire dust
Simulacrum: 1500 gp of ruby dust
Stoneskin: 100 gp of diamond dust

Cheap Stone (No Listed Price):

Darkvision: agate
Disintegrate: lodestone
Erupting Earth: obsidian
Leomund's Tiny Hut: crystal bead
Mending: two lodestones
Moonbeam: opalescent feldspar
Mordenkainen's Private Sanctum: chrysolite powder
Otiluke's Resilient Sphere: crystal sphere
Resilient Sphere: crystal hemisphere
Shatter: mica
Sunburst: sunstone
Wall of Force: crushed clear gem

I like the work you put into that list. I did a similar thing for my notes when setting this up, but I only counted in the groups that gems belonged to (ie: Diamonds and Rubies are the same, both being 5000gp gems), so the goal is to have denominations that either hit those required values exactly, or have denominations that can add up in multiples to hit those targets.
As for gem dust, the only difference between a 50gp Diamond and 50gp or Diamond Dust is the second one is crushed into dust, but otherwise occupies the same volume and weighs the same.
As far as size, even the diameter portion of this is just as a frame of reference. most gems are not going to be spheres, some will have fancy cuts, some will be rough shapes, sphere's are just a simple thing to visualise. The key to it all is just count in the number of coin spaces it occupies.

sandmote

2020-05-05, 12:09 PM

My issue with using gold as a standard weight of coin it that it is far denser than what I expect most people to think of as a typical weight for a piece of metal of a given size. I'd rather compare it to the psychology than individual metals and stones, which I'm aware vary wildly. Compare the described size of gold coins in 5e, which by no real world metric would appear coin-like if made of actual gold. So the standard metal used in the comparison should probably be lighter, to match what most people (including the designers) think of as a reasonable size of metal coin.

250 coins per lb of stone in particular I also have an issue with because the math is more complicated than 100 or 200 coins per lb of stone.

The name categories for each value of gem is a carryover from AD&D 1e's DMG p25 (unfortunately it didn't give details on sizes beyond just saying small, average, large etc), where the values aligned with the values given in 5e. It was just quicker to reuse those terms rather than write out every singe gem.
So Ornate Stones is every gem type in the '10 gp' category, Fancy Stones is everything in the '100 gp' category, etc
All listed forms of Agates are in the '10 gp' group, that's the only reason they would class as Ornate Stones. Carat was definitely the wrong term to use. However, that is the kind of list I was wondering about.

Having now gotten access to the book, I'll repeat the listed stones used as 5e spell components:

Agate: Ornamental
Chrysolite/Peridot*: Fancy (Precious)
Diamond: Gem (Jewel)
Emerald: Gem
Jacinth: Gem (Jewel)
Jade: Fancy
Obsidian: Ornamental
Onyx, Black: Semi-Precious
Pearl, Black: Fancy (Precious)
Pearl, Non-black: Fancy
Ruby: Gem (Jewel)
Sapphire: Gem

*Chrysolite included a number of stone types of similar color until well after the renaissance era.

Looking at the list, I'd drop rubies down to match emeralds and sapphires. Particularly given the book lists a star ruby right next to a star sapphire, each separately without a listed price.

I like the work you put into that list. I did a similar thing for my notes when setting this up, but I only counted in the groups that gems belonged to (ie: Diamonds and Rubies are the same, both being 5000gp gems), so the goal is to have denominations that either hit those required values exactly, or have denominations that can add up in multiples to hit those targets.
As for gem dust, the only difference between a 50gp Diamond and 50gp or Diamond Dust is the second one is crushed into dust, but otherwise occupies the same volume and weighs the same. Because the scaling is linear, right, sorry.

Note to self: in case of pedantry introduce a 1st level transmutation spell that converts cut stones into stones of new shape and equal total size. Costs slots instead of time at the forge, but with an equivalent effect.

Zhorn

2020-05-06, 04:30 AM

Looking at the list, I'd drop rubies down to match emeralds and sapphires. Particularly given the book lists a star ruby right next to a star sapphire, each separately without a listed price.
??? But they do have a listed price (1,000 gp), and also Rubies and Star Rubies are two distinct gems.
Anyway; home games, home rules, adjust as you will.
The system only really needs to worry about setting the baseline volume (size measured in coins) and what the baseline values are (in this case ranging from 10 gp gems to 5,000 gp gems), everything else works itself out from there. You could choose to introduce whole other price categories, and system would work out their values the same way. Example; Add Yellow Diamonds as a 2,500 gp gem.
But for my purposes, I'll just be sticking with the values the book gives.

My issue with using gold as a standard weight of coin it that it is far denser than what I expect most people to think of as a typical weight for a piece of metal of a given size. I'd rather compare it to the psychology than individual metals and stones, which I'm aware vary wildly. Compare the described size of gold coins in 5e, which by no real world metric would appear coin-like if made of actual gold. So the standard metal used in the comparison should probably be lighter, to match what most people (including the designers) think of as a reasonable size of metal coin.

250 coins per lb of stone in particular I also have an issue with because the math is more complicated than 100 or 200 coins per lb of stone.

Doing the math on how much the Draconomicon coins weigh for their volume, and they're not that far off from Iron (~90% the weight).
But again, there's such a huge disparity between real world gem weights that the disparity is comparable to the disparity between metal weights, it can be a bit hair splitting to insist on a particular real world weight on one side of the comparison to a convenient selected for the game weight on the other.
I like 1:5, but I'm still keen to hear from more people as to what ratio sounds better out of 1:5, 1: 2, or some other value.

Tanarii

2020-05-06, 08:35 AM

I found this over at dragonsfoot. It includes some fun stuff about packing densities.

https://www.dragonsfoot.org/forums/viewtopic.php?t=82627

Zhorn

2020-05-06, 09:01 AM

I found this over at dragonsfoot. It includes some fun stuff about packing densities.

https://www.dragonsfoot.org/forums/viewtopic.php?t=82627

Cheers Tanarii, but that's more for the other thread's conversation. I've quoted this over on the other end for the folks there who are interested, all credit to you.

sandmote

2020-05-06, 12:54 PM

??? But they do have a listed price (1,000 gp), and also Rubies and Star Rubies are two distinct gems.
Anyway; home games, home rules, adjust as you will.
The system only really needs to worry about setting the baseline volume (size measured in coins) and what the baseline values are (in this case ranging from 10 gp gems to 5,000 gp gems), everything else works itself out from there. You could choose to introduce whole other price categories, and system would work out their values the same way. Example; Add Yellow Diamonds as a 2,500 gp gem.
But for my purposes, I'll just be sticking with the values the book gives.. For the sake of clarity, the version of the book you referenced that I could get my eyes on lists both price categories and the prices for some individual gems. From there:

2. Black Sapphire: lustrous black with glowing highlights (5,000)
...
11. Ruby: clear red to deep crimson (Corundum) (5,000)
12. Sapphire: clear to medium blue (Corundum)
13. Star Ruby: translucent ruby with white "star" center
14. Star Sapphire: translucent sapphire with white "star" center

Zhorn

2020-05-06, 10:00 PM

For the sake of clarity, the version of the book you referenced that I could get my eyes on lists both price categories and the prices for some individual gems. From there:

Ah, right. Miscommunication. I just got the names for only the categories from 1e, still using 5e's DMG for gem prices, the values of the categories just aligned between editions, but I didn't worry about defining what gems were where in each. That'd just be an over complication.

Unless specified to be from a different source, 5e is what my default is.