Since the days of Pirates! the thought of capturing the Spanish treasure fleet on its way back somewhere in the Spanish Main was a primary target because of all the gold and silver it transported to Spain.

Some of the colonies were rich in gold and silver mines. What seems strange to me is that Potosi was also rich from its mint and that the fleet not only transported raw metal but also coins made from that.

Three examples of many for this scheme are found on the sunken ships from that fleet like the San Jose or the El Salvador, and

enter image description here
The Mercedes trove is on display at ARQUA. VALEROS
Spain’s hard-won shipwreck coins finally go on public display in Cartagena

The simplified usual pattern taught in school is that colonies mostly deliver raw material and the motherlands trade with manufactured goods. This seems the other way around.
That Spanish ships transport coins to Europe seems to be an unquestioned given.

So why didn't they ship exclusively this form:

enter image description here Source: Atocha Treasure Coins

I didn't find any Spanish historical sources that weighed the arguments for either form and I did not find any concrete number that would make a comparison of the relation between pure metal shipped versus coins shipped feasible. That leaves me theorising and without hard number I am sure my imagined relation of both numbers is not even wrong by means of base-rate-error, as I just do not have any good rate or even representative sample over all. The anecdotal Nuestra Senora de Atocha seems to have carried 255000 coins but 'only' "over one thousand silver bars"

Why bother minting the metal in the colonies, increasing its bulk for transport, when the trade was tightly controlled and regulated? Would it not have saved shipping space to only load raw metal? Cargo space is a limiting factor and while it might not matter where a coin is minted, my current reasoning is that using the raw material for shipping it can be transported from every refinery directly to the port, whereas coins need an extra round to the less numerous mints and then to the ports. Refined metal in rectangular shapes should then also take less space on the ships then coins.

Is this more like "doesn't really matter with silver" or are there specific reasons?

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    The whole point is to collect wealth in the mother country. Ship all value home
    – MCW
    Commented Aug 22, 2018 at 11:04
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    presumably they were minting the coins for local use as well, and thus had the capability once that is the case, you'd have to see what the capability in spain for minting was, and the relative costs.
    – user31561
    Commented Aug 22, 2018 at 11:14
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    At least after Newton, a coin was supposed to be worth more than the raw metal value. As such, your argument about value per volume of cargo may fail. Commented Aug 22, 2018 at 13:56
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    @CarlWitthoft Not in every case, like Kopeks or : The penny might be more trouble than it’s worth. But point taken. I had to speculate, hence I am asking here ;) If you could sustain your argument and apply it to the concrete situation, then by all means, answer disproving my theory… Commented Aug 22, 2018 at 14:01
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    @DavidRicherby That's bullionist theory. As can be seen in Alberto's answer as well, the actual content of precious metal fluctuated and might have been better the one or worse at another point in time. Cf Denarius in Debasement, long before Newton. Commented Aug 22, 2018 at 15:24

7 Answers 7


According to Manuel Moreyra Paz Soldán, El Virreinato de Perú, 1980, p. 79, the coinage embarked on ships corresponded to:

  • Taxes obtained from the provinces and citizens in America: "recaudación para la Real Hacienda".
  • Salaries from workers and sailors: "cajas de soldadas, incluyendo de la tripulación"
  • Money to pay the expenses of the voyage: "talegas para los puertos habilitados para el comercio de Indias"
  • Coins sent by private citizens: "bienes embarcados a nombre de particulares".

Spain also suffered several coinage crisis during the 17th and 18th centuries that reduced the amount of silver in the coins (called "de vellón" (goldish) because they had a lot of copper to compensate).

The coins coming from America were more appreciated due to their purity in silver. In fact, they used to leave the country so fast towards Europe that they made the crisis in Spain even worse.

  • +1 Especially the last one was on my list of possibilities. But does your source have any comparison in numbers for amount of raw material shipped in relation to the coins? I imagine the first point to be easily transformed via internal calculations while the other three might be quite a bit smaller than raw exports. Commented Aug 22, 2018 at 11:19
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    @LangLangC It doesn't provide a percentage, but the reports of the ships were available online when there was all the fuss about Odissey not wanting to sell the coins to the Spanish Government. I suppose you could look for them. I guess that when the mint house of Lima opened in 1684, the amount of silver coins sent to Spain increased a lot. After 1650 the amount of ingots of silver Spain received was much smaller (and the gold was almost non existant). Commented Aug 22, 2018 at 15:01
  • It makes sense. Spanish America had a lot of people, planned cities, local mayors and viceroys, religious orders, even universities. If there were no coins locally, paying salaries, building, and collecting taxes would be difficult. Also: the coins also left for Asia via Philippines. The Chinese were also fond of Spanish coins.
    – Luiz
    Commented Nov 18, 2020 at 11:50

I'm hoping that this answer will resonate with your "theory of colonial economy", although it is not based on historical sources.

Coins shouldn't be viewed as end products manufactured from a raw material. The metal is minted primarily to provide a standard way to quantize and control the content (amount) of the precious metal during circulation. For that reason it is often practical to place a mint close to a mine and manage the two as a secure unit. The coin form essentially promises that the inside is the same metal as the outside and that no part of the treasure was stolen or replaced on the way.

Therefore, knowing how much value was being transferred to Europe might have been practical enough for the transport itself.

Even if the "raw material" is shipped - that is, gold or silver, as distinct from various ores, it is practical to employ standardized precious metal content, standardized weight, standardized shapes. In the end a bar of gold is just a bigger coin.

Ores are too bulky to be transported for long distances. Extraction of the metal reduces weight enough for making it efficient to do so before carrying the material overseas.

Assorted "Golden items" from pre-colonial items were rarely made of gold, but more typically using metallurgic techniques that give you gold on the outside, copper in the inside. Such "manufacture" does not count in our context.

Therefore I'm not surprised that coins were frequently included as a method of getting some silver home.

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    Good answer! You could also add the density problem; if you fully packed a ship with gold, it would sink pretty quick. So half-density gold (or silver) becaues they are coins isn't a problem on a ship.
    – Yakk
    Commented Aug 22, 2018 at 15:44
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    I particularly like the point that transporting unrefined ore amounts to hauling a lot of useless weight across an ocean.
    – T.E.D.
    Commented Aug 22, 2018 at 15:46
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    "The coin form essentially promises that the inside is the same metal as the outside and that no part of the treasure was stolen or replaced on the way." Although it might be worth noting that the promise was not always kept. See Francisco Gómez de la Rocha, mayor of Potosí and executed for defrauding the crown. Commented Aug 22, 2018 at 16:08
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    @Yakk - You've done well to expand your comment into one of the great four top voted answers that complement each other. Commented Aug 25, 2018 at 11:56

Many of the coins shipped to Europe were quickly and crudely minted. These were called cobs. According to a page at Notre Dame University,

The intention in minting these crude but accurately weighed cobs was to produce an easily portable product that could be sent to Spain. In Spain the cobs would be melted down to produce silver jewelry, coins, bars and other items. Cobs also circulated as coinage, many cobs made their way to the English colonies where they were used both as coins in commerce and hoarded as specie.

My interpretation of that passage as it relates to your question is that coins were easier to disburse upon reaching their destination. Bars would have to be melted or cut into accurately weighted pieces, and the traders who transported them may not have had the expertise to do this.

  • I loved learning about this. And source quoted in the answer continues "As the cobs were crudely produced it was quite easy for colonials to clip off some silver and then pass the coin off at full value.", thus showing that even pseudo-coins optimized for state-controlled bulk transport and re-minting, rather than for general circulation, could frequently be coin-sized. Commented Aug 24, 2018 at 14:31

Gold and Silver are worth so much that their "bulk" is very rarely a problem.

Coins make it easier to count them. Their bulk is increased slightly; say by a factor of 2.

This makes gold 10 g/cm^3 and silver 5 g/cm^3.

Now, a ship's hold has to be significantly under 1 g/cm^3 in order for the ship to float (otherwise the interior of a ship is heavier than water; that won't do). For both gold and silver coins, the space that they take up is essentially zero; doubling their density (by having gold or silver blocks) wouldn't improve your cargo handling characteristics.

If the hold must be at 0.5 g/cm^3. Solid gold then would take up at most 2.5% of the hold. If we allocate 2% of the hold to solid gold, the remaining material must have a density of no more than 0.102 g/cm^3. If we allocate 4% of the hold to gold coins, the remaining density of the hold must be no more than 0.104 g/cm^3 and have the same weight: there is no noticable difference.

This holds similarly for silver vs silver coins; both gold and silver and coins are so dense that they take up no noticable volume on an ocean going ship.

Minted coins are easier to count and they have a "trademark" that signifies their quality. The limit on carrying them is going to be weight.

You have to refine your gold/silver anyhow (you aren't going to ship ore), and using coin molds isn't much harder than some kind of solid block.

As an aside, one of the most dangerous thing to ship on the Mississippi back when it was the highway of the USA was pig iron. It is dense (8 g/cm^3) and if it shifted it could knock a hole in the bottom of the boat or cause the ship to tip and sink.

Reducing the density of the metal to coins may be a good thing and make it easier to ship.

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    Casting into coin molds is much harder than just pouring an ingot. But faking one ingot is (worth the risk) a lot easier than faking a chest full of coins.
    – Mazura
    Commented Aug 24, 2018 at 22:30
  • Even back in the 1700s people rarely had the funds to buy a whole 25 kg bar of silver but bought the silver needed for one or two pieces of jewelry.
    – Trish
    Commented Aug 25, 2018 at 16:36

Another reason for local coinage, in addition to the excellent points above, is that the Viceroyalties were large economies on their own. The Mexican mint was founded in 1535, before the colony's silver mining sector was developed. The imperial bureaucracy depended upon a standardized means of exchange.

Even though Mexico suffered a lack of monetary liquidity for centuries, it would have been even worse off without that mint. Spain was not too interested in exporting specie to its colonies.

  • It would be nice to see a book on this. I'm having trouble wrapping my mind around how astute this action was, and how far-reaching the consequences were. For instance, I understand it was the mid 19th century before its currency quit being legal tender in the USA.
    – T.E.D.
    Commented Aug 23, 2018 at 13:26
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    @T.E.D. A good review of imperial macroeconomics is in the paper The Spanish Empire and Its Legacy: Fiscal Re-distribution and Political Conflict in Colonial and Post-Colonial Spanish America (Grafe & Irigoin) Commented Aug 23, 2018 at 16:22

On another note, a lot of the Silver mined in Spanish Colonies actually never was sent to Spain, a lot of the treasure fleets directly sailed for the Philippines for a period, because Spain used a lot of the silver to trade with China anyway.

John Gareth Darwin talked about this in After Tamerlane, called the Manilla Galleons for the harbour they used, sailed for ~250 years from Manila to America between 1565 & 1815.


Too long for a comment, but a few points apparently missed from all the other answers from Wikipedia on Gold Extraction:

Gold occurs principally as a native metal, usually alloyed to a greater or lesser extent with silver (as electrum), or sometimes with mercury (as an amalgam). Native gold can occur as sizeable nuggets, as fine grains or flakes in alluvial deposits, or as grains or microscopic particles (known as color) embedded in rock minerals.

In consequence, most New World gold mining would have been placer mining:

the mining of stream bed (alluvial) deposits for minerals. This may be done by open-pit (also called open-cast mining) or by various surface excavating equipment or tunnelling equipment.

Some of the techniques for (19th century) hydraulic-mining of surface gold are well depicted in the movie Pale Rider, though techniques available before steam engines would have been slower and more crude, with only gravity available as a sufficient energy source

Note that the vast majority of gold occurs as either native metal (ie nuggets) or alloyed with other precious metals; and the minting process then requires very little, and often close to zero, actual refinement.

As a final melt was necessary in any case, to produce objects more easily handled than miscellaneous-sized nuggets (remember, gold is heavy) the choice of pouring into ingot-moulds or coin moulds is really rather arbitrary. Transporting the nuggets as is is a false choice, quite impractical.

The processes by which lower-grade ores could be smelted for their gold weren't developed until 1783 (solubility in a cyanide-water solution) and 1887 (MacArthur-Forrest Process capable of achieving 96% purity from ore). Prior to that time the principle techniques for pre-smelting and smelting basically mimicked the natural production of placer gold, producing odd sizes of gold nuggets.

Ores in which gold occurs in chemical composition with other elements are comparatively rare. They include calaverite, sylvanite, nagyagite, petzite and krennerite.

  1. History of Gold Refining
  2. The Gold Smelting Process
  • 1
    An interesting "new" perspective.
    – Tom Au
    Commented Dec 11, 2020 at 18:40

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