Draconomicon: HOW BIG IS THE PILE? - How big was Smaug's hoard really? [Archive]

Necroticplague

2014-09-12, 02:16 AM

In the 3.5 Draconomicon on page 278 there is a sidebar titled "HOW BIG IS THE PILE?" wherein the actual maths for the size and composition of dragon hoards is discussed.

I remembered this today and caught myself wondering if anyone had thought to apply it to the dwarven treasure piles that composed Smaug's hoard in the 'The Hobbit' movie?

Also curious how much that hoard would be worth in D&D 3.x/PF terms.

We had a bit on this in the Dysfunction thread. At the most conservative estimate, a hoard that massive contains essentially Treasure: all of it. a 50,000 GP hoard could be crammed into a reasonably large backpack (assuming it could support the weight), even after accounting for the fact that it seems that gold in dnd is about one-third as dense as it is in real life (based on the size given for a gold coin in the same book, combined with earlier books stating it was 50 GP to a pound).

SciChronic

2014-09-12, 02:31 AM

Necroticplague

2014-09-12, 02:44 AM

its probably reasonable to say that gold coins aren't pure gold, as it'd be too malleable to use as actual currency, and it'd be difficult to purify gold ore without magic. it'd probably an alloy composed of lighter metals such as tin, iron, zinc, with gold mixed in creating the color.

According to Wealth and Money (http://www.d20srd.org/srd/equipment/wealthAndMoney.htm), a pound of gold costs 50 GP, and 50 GP weigh a pound. That seems to make a strong case for GP being pure gold.

Gwendol

2014-09-12, 02:54 AM

its probably reasonable to say that gold coins aren't pure gold, as it'd be too malleable to use as actual currency, and it'd be difficult to purify gold ore without magic. it'd probably an alloy composed of lighter metals such as tin, iron, zinc, with gold mixed in creating the color.

Of course it's pure gold, otherwise it would not be gold coins, but alloy coins.

avr

2014-09-12, 02:59 AM

SciChronic

2014-09-12, 03:08 AM

Of course it's pure gold, otherwise it would not be gold coins, but alloy coins.

We don't say nickel alloy coins either (the composition of a US Nickel is 25% nickel and 75% copper, so it'd actually be a copper alloy coin).

9K gold is only 38%, but we still say it's gold.

Necroticplague

2014-09-12, 03:14 AM

We don't say nickel alloy coins either (the composition of a US Nickel is 25% nickel and 75% copper, so it'd actually be a copper alloy coin).
That's because our coinage is 100% fiat currency, where the value of the metal has no bearing on its value. The fact dnd has universal currency (I.E, it doesn't ever mention exchange ratios, or different types of gold coins), however, strongly implies the GP is not similarly fiat (in addition my my above-mentioned implication).

Gwendol

2014-09-12, 03:40 AM

See: http://en.wikipedia.org/wiki/Guinea_(British_coin)

Not antique coins, but the purity of the gold is fairly high.

Seharvepernfan

2014-09-12, 03:45 AM

I did some math once (I dont recommend it). My house is a bit on the large size; 15 rooms. If I filled every inch of space inside this house with perfectly stacked pennies, it could hold at least 4 billion pennies. More than I could count in an entire lifetime.

Now, a penny is smaller than a gold coin. Let's say a gold coin is about 8 pennies in total size (4 stacks of two). So, about 500 million in my house. The mountain of coins in smaugs lair was the size of a town. Did you pay attention to the background in that scene? It's literally thousands of feet in one direction, and it's all one big pile.

Now, we don't know how deep that pile is. It could just be covering the floor of a sloping cavern, I dunno.

Still, I'd guess it's between 500 billion and a trillion coins - just off the top of my head. I'd say there was a thousand of my house's in space in that pile, ballpark.

hamishspence

2014-09-12, 06:10 AM

We had a bit on this in the Dysfunction thread. At the most conservative estimate, a hoard that massive contains essentially Treasure: all of it. a 50,000 GP hoard could be crammed into a reasonably large backpack (assuming it could support the weight), even after accounting for the fact that it seems that gold in dnd is about one-third as dense as it is in real life (based on the size given for a gold coin in the same book, combined with earlier books stating it was 50 GP to a pound).

Did the book specify the thickness of the coin?

If it did - there's one way to reduce the density of the coin while still keeping it "pure gold" - air spaces.

ILM

2014-09-12, 06:46 AM

There's a ridiculous amount of gold there. If it was about 10 000 cubic metres that's about 19 300 tonnes, so about 42 000 000 pounds or 2 100 000 000 GP. Call it a few billion.
Draconomicon, in the part about getting a Dragon as cohort or mount, also mentions the hoard should be 1,000 gp per HD, which makes Smaug very, very, very epic. :smalltongue:

Ketiara

2014-09-12, 06:51 AM

There's a ridiculous amount of gold there. If it was about 10 000 cubic metres that's about 19 300 tonnes, so about 42 000 000 pounds or 2 100 000 000 GP. Call it a few billion.

Not that Smaug or Thorin would ever spend any of it.

10 000 m3 = 50m x 50m x 4 m deep area. It could easily be more.

And the total amount of gold excavated in the world could fill a cube of 21 meters. So yes its a ridiculous amount of gold :D

Heliomance

2014-09-12, 07:00 AM

ngilop

2014-09-12, 07:00 AM

Draconomicon, in the part about getting a Dragon as cohort or mount, also mentions the hoard should be 1,000 gp per HD, which makes Smaug very, very, very epic. :smalltongue:

Forbes does a list of fiction rich people every year
http://www.forbes.com/pictures/mlg45edmmd/2-smaug/

this is not the indepth explanation of the rankings, but from what I remember for an earlier version, wherein smaug ranked #1, smaug was measured using the draconomicon and came out to b very tiny. id wish they would have usd 2nd ed measurements for smaug and not the barely 80 foot of body length draconomicon gave him ( in the novels he wa MASSIVE)

plus it just measured the pile of coins that smaug slept on, disregarding the urns filled with treasure and other such wealth lieing around.

Necroticplague

2014-09-12, 07:04 AM

Did the book specify the thickness of the coin?

If it did - there's one way to reduce the density of the coin while still keeping it "pure gold" - air spaces.

Yes, it did. It said that go we're slightly over an inch across by a tenth of an inch thick. Of course, if you simply take the amount of gold in a pound and divide it by 50, you get that it has twice the volume of a dime. So, in order to make these two figures meet, apparently gold coins are pretty much hollow.

Thurbane

2014-09-12, 07:10 AM

Are the gold coins African or European?

Lord Vukodlak

2014-09-12, 07:13 AM

According to Wealth and Money (http://www.d20srd.org/srd/equipment/wealthAndMoney.htm), a pound of gold costs 50 GP, and 50 GP weigh a pound. That seems to make a strong case for GP being pure gold.

This would be why D&D currency is universal

Yes, it did. It said that go we're slightly over an inch across by a tenth of an inch thick. Of course, if you simply take the amount of gold in a pound and divide it by 50, you get that it has twice the volume of a dime. So, in order to make these two figures meet, apparently gold coins are pretty much hollow.

When designing a new currency system that added more flavor without adding more book keeping. I ran some numbers and a gold coin weighing 1/50th of a pound would be roughly the size of a penny.

hamishspence

2014-09-12, 07:35 AM

from what I remember for an earlier version, wherein smaug ranked #1, smaug was measured using the draconomicon and came out to b very tiny. id wish they would have usd 2nd ed measurements for smaug and not the barely 80 foot of body length draconomicon gave him ( in the novels he wa MASSIVE).

In the art for the novel's first edition though, he's pretty small.

Segev

2014-09-12, 07:52 AM

I'm personally of the opinion that dragons are great fans of the Fool's Gold spell, and use it on a lot of copper coins. (Said spell seems not to be in 3e; in 2e, it was an illusion that made other metals into convincing - but not perfect - forgeries of gold.)

But more seriously, consider that most coins in circulation will be silver or (even more commonly) copper. Burnished copper can appear gold in the right light.

Admittedly, 500 billion copper coins is still 5 billion gp worth of loot, but it does make it less astronomical in value.

As for Smaug and King Thorin, perhaps Lonely Peak truly had that much gold available to mine, and the dwarves industriously acquired it. But they hoarded it for the same reason DeBeers hoards diamonds: it keeps gold valuable in the outside world, thus making their reserve technically worth so much more. It effectively allowed the King Under the Mountain to transform gold into a fiat currency that HE controlled the world over. No wonder he got a reputation for insane greed amongst other races: he had truly seemingly limitless wealth, and he negotiated like he was on a sharp budget. Because he was, but it was a hidden, hard-to-calculate one: how much gold can I spend without devaluing it noticeably?

Smaug, of course, isn't spending it and never will. It's his, and he doesn't want anything more than he wants his hoard. Beside, he can just take what he wants, if he wants something more.

But for D&D dragons, consider making the hoard out of art objects, suits of gilded armor (lots of air pockets and lighter metals to add bulk), semi-precious gems, and copper coins.

Also, I think I'm doing my research wrong, as even the tiny coins described here on the boards are sounding too big. If you melted down the 50 gp that supposedly make up a lb of gold, and poured it into a cube, how big would that cube be? My brief research is telling me that a cubic inch of gold would weigh roughly 0.7 lbs, which means you'd have to be able to get just under 35 coins from a single cubic inch.

Which, I suppose, is just shy of making the coins 1/16" thick, 1" long, and .5" wide. Reshape that a little bit and you wind up with a 0.79788 inch diameter coin that is just shy of 1/16" (0.0625 in.) thick. A US penny is 0.75 in. in diameter, and 0.05984 in. thick. So a gold coin, at 50 gp to a pound, would be just about the size of a US penny.

That's not too unreasonable.

Back to dragons, though: D&D dragons probably have copper piece hoards that are very highly polished.

bjoern

2014-09-12, 08:45 AM

And the total amount of gold excavated in the world could fill a cube of 21 meters. So yes its a ridiculous amount of gold :D

No way. Really?

All the gold found in the history of the world is only 21m cube? That's crazy. That's not much at all.

nedz

2014-09-12, 09:00 AM

Are the gold coins African or European?

That question is only relevant if you want to know how far you can throw them. Besides Smaug's gold coins were Dwarven.

The Insanity

2014-09-12, 09:11 AM

Maybe the coins have a hole in them like this?
http://thumbs.dreamstime.com/z/chinese-new-year-dragon-gold-coin-21381206.jpg

Dalebert

2014-09-12, 09:17 AM

If it did - there's one way to reduce the density of the coin while still keeping it "pure gold" - air spaces.

Allow me to ruin the joke by explaining the humor of the sarcasm here. That would add a tremendous amount of extra work to mint the coins while at the same time reducing their value and making them bulkier. It would be less than pointless. It would actually run counter to a primary goal of currency which is to pack a lot of value into something relatively compact and light and easy to carry. The only people who might do this would be counterfeiters, but it would even run counter to their goals because it would be far easier to put some heavy material inside and most anything that is as dense as gold is also more valuable. Therefore, not even counterfeiters would do this. They would use a cheap and heavy material (but not as heavy as gold) and HOPE that people don't weigh the coin.

Of course it's pure gold, otherwise it would not be gold coins, but alloy coins.

Like electrum? Most people will recognize that from 2E as a gold and silver alloy metal which was also fairly common coinage.

its probably reasonable to say that gold coins aren't pure gold, as it'd be too malleable to use as actual currency, and it'd be difficult to purify gold ore without magic. it'd probably an alloy composed of lighter metals such as tin, iron, zinc, with gold mixed in creating the color.

It's not a reach at all that they purify it without magic. That's what smelting is all about. I don't want to pretend I know the details but I'm sure it has to do with different metals separating out when you get them to liquid form based on density, and gold is quite dense. Lighter metals (and as I pointed out, most metals are lighter unless they're more rare and valuable even than gold) could be skimmed off the top fairly easily to result in a very high purity of gold.

And yes, probably an alloy, but still probably mostly gold. There are countless gold coins used in circulation that were very high in purity, i.e. about 90%+, including American Gold Eagles. That was back before they hoarded all the actually inherently valuable money and replaced it with FIAT money (mostly paper but also some crap coinage) that has been declared to have value "because we say so". You can still buy them as an investment. They're stamped with their value at the time--about $20, despite now being worth exponentially more just for their gold value. In fact, they keep having to change the composition of modern coinage because the metal keeps being worth more than the actual coin due to rapid inflation, i.e. printing more money to pay their bills so that the total value of all the money goes down. It's one of the most discreet (that's a nice word for it) methods of taxation. Pennies have hardly any copper in them and older pennies are actually worth several times a penny in copper value alone. Most knickels are worth more than a (FIAT) knickel. They're actually losing money minting a lot of coinage and they frequently discuss ending the minting of pennies altogether.

All the gold found in the history of the world is only 21m cube? That's crazy. That's not much at all.

And hence why it's so valuable. The metal also has nice properties, and that's part of it, but scarcity is a huge factor.

hamishspence

2014-09-12, 09:28 AM

Allow me to ruin the joke by explaining the humor of the sarcasm here. That would add a tremendous amount of extra work to mint the coins while at the same time reducing their value and making them bulkier. It would be less than pointless.

They don't have to be on the inside- they can be on the outside. Intaglio designs.

And yes, it does make the coins bulkier - but that makes it easier for them to take up the specified amount of space.

Fouredged Sword

2014-09-12, 09:41 AM

A
It's not a reach at all that they purify it without magic. That's what smelting is all about. I don't want to pretend I know the details but I'm sure it has to do with different metals separating out when you get them to liquid form based on density, and gold is quite dense. Lighter metals (and as I pointed out, most metals are lighter unless they're more rare and valuable even than gold) could be skimmed off the top fairly easily to result in a very high purity of gold.

The easiest (low tech, fairly effective) method is to separate the ore using mercury before doing a skim process as you suggest. You break the ore into tiny pieces and float it in a tub of mercury. The gold is heavier, so it sinks. The rock and other metals all float. Then you melt the metal and skim the surface to remove any impurities to the gold itself.

Nasty process though. You end up cooking off mercury while melting the gold, causing everyone involved to be horribly poisoned. We didn't figure that out for a long time though.

There IS not such thing as 100% purity unless you are dealing in clean room conditions or very small amounts though.

Segev

2014-09-12, 09:44 AM

Not to derail too much, but I've occasionally thought it would be interesting to see a government which only taxed via fiat currency. That is, they very carefully printed more money each year as their budget, and relied on the obsolecence of old currency (that is, money that gets lost or destroyed by day-to-day use) to combat inflation, they would tax their people uniformly. They could also use fees and licences and the like (which at least US federal and state governments typically have) as ways to collect currency to combat it.

This actually goes back to what I hypothesized might be what the King Under the Mountain was doing: he had a stockpile of gold that was artificially valuable because he had more of the supply than existed in the whole rest of the world. So he could control that value by keeping it hoarded.

nedz

2014-09-12, 10:15 AM

Segev

2014-09-12, 10:18 AM

Similar things have been done, the result is called hyper-inflation.

The problem is that it is done in conjunction with taxation by governments with no fiscal responsibility. We have yet to see one that exercised any sense of fiscal responsibility trying to do it. Of course, ASKING politicians to work within a budget is kind-of like asking orcs not to pillage. Sure, they're capable of it, but why would they?

And the dirty secret is that the US government's been doing it for years. While taxes bring in a lot of revenue, more comes from borrowing and fiatting more (we don't even print it anymore; we just say we've borrowed it and transfer it into bank accounts). The effect of those loans is really the same as printing it in the short term; there's more money in the system than there was before. Unless and until it's paid back, anyway.

ANd now I'm really drifting off topic. Sorry. ^^;

avr

2014-09-12, 10:34 AM

FWIW I dropped a decimal place above. 193 000 tonnes & so 21 billion GP.

Fouredged Sword

2014-09-12, 11:57 AM

The problem is that it is done in conjunction with taxation by governments with no fiscal responsibility. We have yet to see one that exercised any sense of fiscal responsibility trying to do it. Of course, ASKING politicians to work within a budget is kind-of like asking orcs not to pillage. Sure, they're capable of it, but why would they?

And the dirty secret is that the US government's been doing it for years. While taxes bring in a lot of revenue, more comes from borrowing and fiatting more (we don't even print it anymore; we just say we've borrowed it and transfer it into bank accounts). The effect of those loans is really the same as printing it in the short term; there's more money in the system than there was before. Unless and until it's paid back, anyway.

ANd now I'm really drifting off topic. Sorry. ^^;

This is an oversimplification. The US does generate fait currency out of thin air, but it does so in a very regular and predictable manner. It would be much like the king owning a gold mine. Yes, everyone knows the king is going to get "free" gold, but he will do so in a limited and predictable manner. The fact that there is gold entering and expanding the gold supply does not wreck the value of the gold that currently exists. The US prints and borrows money roughly in step with the US economy, with deviations caused by wars (rapid temporary increases in spending) and recessions (rapid slowdowns in GDP growth)

Segev

2014-09-12, 01:54 PM

This is an oversimplification. The US does generate fait currency out of thin air, but it does so in a very regular and predictable manner. It would be much like the king owning a gold mine. Yes, everyone knows the king is going to get "free" gold, but he will do so in a limited and predictable manner. The fact that there is gold entering and expanding the gold supply does not wreck the value of the gold that currently exists. The US prints and borrows money roughly in step with the US economy, with deviations caused by wars (rapid temporary increases in spending) and recessions (rapid slowdowns in GDP growth)

If the US (or another hypothetical government) were to remove all taxes and simply paid all of its bills with money printed in a "regular and predictable manner," that would not then change the above scenario all that much. One could even mandate that it be based on economic numbers (provided one could trust the government not to doctor the calculations, but really, we have to trust that at some point anyway).

One could even "borrow" against future "regular and predictable" fiat printings, promising oneself to not print as much as one could in the future to make up for a temporary spike (like, say, due to war).

Going back to the King with the gold mine analogy, this would be like borrowing against future gleanings from the mine. "I will pay you back with what comes out next year if you loan it to me today."

Obviously, these "loans" to oneself would have to be very strictly monitored. Spending would have to be very, very carefully regulated and kept under control. But fiat currency printings based on a strict percentage of the GDP as the sole source of "tax revenue" would be the least painful way for the government to harvest money from the populace, I think. It would, in fact, be just like the Dwarf King maintaining a gold mine that was his exclusive royal property and funding the government out of its proceeds.

Necroticplague

2014-09-12, 05:51 PM

When designing a new currency system that added more flavor without adding more book keeping. I ran some numbers and a gold coin weighing 1/50th of a pound would be roughly the size of a penny.

I ran similar numbers as well, and ended up with it being smaller .Look at this (http://www.giantitp.com/forums/showthread.php?333789-Dysfunctional-Rules-Thread-V-Dysfunctions-All-the-Way-Down/page45) and the next few pages where we talk about it.

Stella

2014-09-12, 06:11 PM

Smaug, of course, isn't spending it and never will. It's his, and he doesn't want anything more than he wants his hoard. Beside, he can just take what he wants, if he wants something more.He really can't, not having any means to move his property from one area to another (I'm going to assume that "not even mend a little loose scale of their armour" means that dragons use no tools and possibly don't even have an opposable thumb, which would limit their ability to transport their hoard to whatever they managed to get stuck in their scales over a few hundred years time of lying on top of it.). This is exactly why Smaug took the Lonely Mountain, it was the largest hoard he could possibly claim for his own.

Dragons steal gold and jewels, you know, from men and elves and dwarves, wherever they can find them; and they guard their plunder as long as they live (which is practically forever, unless they are killed), and never enjoy a brass ring of it. Indeed they hardly know a good bit of work from a bag, though they usually have a good notion of the current market value; and they can't make a thing for themselves, not even mend a little loose scale of their armour. ... There was a most specially greedy, strong and wicked worm called Smaug.

If the US (or another hypothetical government) were to remove all taxes and simply paid all of its bills with money printed in a "regular and predictable manner," that would not then change the above scenario all that much. One could even mandate that it be based on economic numbers (provided one could trust the government not to doctor the calculations, but really, we have to trust that at some point anyway).

One could even "borrow" against future "regular and predictable" fiat printings, promising oneself to not print as much as one could in the future to make up for a temporary spike (like, say, due to war).
This might work in some other government, hypothetical or not, but not the US government. No Congress is allowed to limit the powers of any future Congress per the Constitution, which is far more difficult to enact a change to than any law. So no matter how fiscally responsible (*snerk!*) any given Congress might be during their own terms, they cannot pass any laws or rules which will force any future Congress to honor any plans or promises they laid down during their own terms.

Dalebert

2014-09-12, 07:05 PM

They don't have to be on the inside- they can be on the outside. Intaglio designs.

And yes, it does make the coins bulkier - but that makes it easier for them to take up the specified amount of space.

Okay, that would make it easier. Doesn't change the fact at it would be ridiculous to arbitrarily make coins take up more space. That would still run counter to a primary goal of currency which is to store a lot of value in a compact space. It would be like making a bucket with small holes to make sure people didn't carry TOO much liquid in it.

Rubik

2014-09-12, 07:15 PM

Are the gold coins African or European?Depends on how they're swallowed.

Segev

2014-09-13, 12:31 AM

This might work in some other government, hypothetical or not, but not the US government. No Congress is allowed to limit the powers of any future Congress per the Constitution, which is far more difficult to enact a change to than any law. So no matter how fiscally responsible (*snerk!*) any given Congress might be during their own terms, they cannot pass any laws or rules which will force any future Congress to honor any plans or promises they laid down during their own terms.
Oh, I know. This would require an amendment to the Constitution, because it would require changing the fundamental way the US government raises and spends money. (Much as the 16th amendment was needed for income tax to become how it's done, now.)

Stella

2014-09-13, 02:43 AM

Yeah. And this can be a good thing and a bad thing all at the same time. For example it allows Congress to change the age of benefits for Social Security as the natural life expectancy of people increases due to medical advances. But it also allow Congress to say "Hey, we haven't had a crisis concerning unregulated banking and investing for quite some time, so the public (and we in Congress, of course) has pretty much forgotten about this issue. And deregulating banking and investing is something which our major campaign contributors are pushing for. So it must be a great idea to deregulate banking and investing!", which lead to the financial collapse of 2007-2008.

unseenmage

2014-09-16, 03:40 PM

Are the gold coins African or European?

Depends on how they're swallowed.

Thanks for making me smile you two.

More to the point, I remember reading about coin shaving and moneylenders in either Power of Faerun or Arms and Equipment? Not sure which. Was quite the long entry on how coinage realism could be done and why no two coins from the same moneylender would be the same let alone from the same era or country or generation.

So I view the coin stats by RAW or by what we can calculate as a rough average of what a gold coin is in the gameworld. Which still doesn't make the discrepancies go away but might soften them some.

As to the nearly immesurable volume of physical wealth being generated by a single mine/civilization. Remember that in the D&D verse matter destruction is a thing. One Sphere of Annihilation or Bag of Holding/Pot. Hole mishap and it's all (or next to nearly all) gone.
And that in the LotR universe maybe striking volcanic vents is a thing for the dwarven communities. This is just conjecture and is undone by the whole Gandalf falling through the center of the world with the Balrog thing. But hey, maybe vast centers of limitless wealth can be disappeared. Maybe trolls eat gold or some other mystical force changes it from being a limitless supply of an eternal resource into a limitless supply of a consumable resource.

Dalebert

2014-09-16, 04:00 PM

I'm surprised no one has yet mentioned the titan-sized statue of solid gold they made that melted and created a giant river of molten gold that filled the castle and then some.

I think we can reasonably conclude--it was a frackin' lot o gold! They were shooting for epic levels of wealth. Remember from the book that Bilbo was entitled to some ridiculous chunk of it and was quite content with a couple saddlebags full and he was wealthy for a long life with plenty to leave to Frodo. Maybe he had some gems and such too but I seem to recall it being mostly gold. I think it's safe to say that D&D devalues gold, though I understand why. It would feel underwhelming to find a chest of treasure and it has maybe 5 gold coins in it. It's a way of letting you feel like you just found a treasure hoard without you feeling like you can just retire (like Bilbo) and quit adventuring.

Lord Vukodlak

2014-09-16, 06:38 PM

I ran similar numbers as well, and ended up with it being smaller .Look at this (http://www.giantitp.com/forums/showthread.php?333789-Dysfunctional-Rules-Thread-V-Dysfunctions-All-the-Way-Down/page45) and the next few pages where we talk about it.
A penny has a diameter of 19.05mm and a thickness of 1.52mm. This gives us a volume of 433.23mm3 or .43323cm3 multiplied by the density of gold 19.30g/cm3 and you have 8.36 grams which is 1/55th of a pound, which is close enough.

Biffoniacus_Furiou

2014-09-16, 07:14 PM

D&D gold is 50 coins per pound, so 1 gp is 0.32 ounces, or about 9 grams. A British Guinea that weighed 8.4g had a 25mm diameter (http://www.royalmint.com/our-coins/ranges/guinea), which is just barely under 1 inch. So a 9g gold coin should have a diameter of about 1 inch, assuming it's relatively the same thickness. This should be fairly consistent with Tolkien's idea of the size of a gold coin, so the gold coins of the dwarves of Middle Earth should be more or less equal to the gold coins of D&D.

This Wired article (http://www.wired.com/2013/11/does-smaug-have-enough-gold/) (making a lot of assumptions) came up with a result of 2.69 x 10^6 kg (2.69 million kg), which happens to be more gold than has been mined on the Earth since 1880. Add another three zeroes to get grams, divide by nine, and we have 298,888,888 gp, so we can pretty safely estimate that Smaug has three hundred million gold pieces.

Edit: Just to note, the sample dragon hoards in the back of the Draconomicon values a CR 27 dragon hoard at 465,000 gp. Dragons get triple standard treasure, so according to the ELH rewards on page 122, and expanding the list as best I could, this should be a CR 48 dragon hoard in coins alone, not counting the various art objects or gems. An Old Prismatic Dragon is CR 48, a Wyrm Force Dragon is CR 50. So a hoard of this size could easily exist in an epic level game of D&D.