Well, one way they could do it is to use a file, essentially a tool-steel bar with an abrasive surface, and rub it against the surface of an ingot of silver. This would produce a relatively fine powder though it would be a painfully long process to get a lot of it.

Another option is to dissolve some silver in Aqua Regia, a mixture of hydrochloric acid and nitric acid. Adding urea will then consume the residual nitric acid and ferrous sulphate to precipitate fine silver powder which can be filtered out of the solution. Assuming the Romans had access to these chemicals, they could use them in order to create a very fine silver powder. One thing to note, silver is resistant to Aqua Regia at room temperature. In order for the silver to be broken down, the temperature, pressure, or concentration of acid must be changed. Here is a link to an answer on Chemistry.SE which explains it.

Roman age? I can give you a stone age method: Grind it between two rocks.

Silver has a mohs hardness of 2.5. Granite has a mohs hardness of 6-7. So you can use a rough granite stone to grind silver to dust. It might take a while and take some muscle, but it should work.

When you are lazy, you might try to just throw your silver into a grain mill. It should work if the millstones are from a mineral which is harder than silver and if the mechanics are sturdy enough to handle the stress. The Romans had water-powered mills since the 1st century.

The trip hammer was historically used for this

First, this process is called comminution. In the most ancient of days, to break up an ore into small chunks to work it in a forge, you simply hit it with a rock hammer. Eventually, the process improved until some sort of mechanical power could be applied: enter the trip hammer.

Image source.

A water-powered trip hammer is essentially a very large hammer, mounted on a fulcrum, with one end (the helve) moved by a cam. The cam is in turn driven by a water wheel. Alternative, you could have a donkey or ox provide the motive force, though there isn't a lot of evidence that this happened. There is significant mechanical loss in older mechanical systems, lubricated with animal fat and made of wood. A donkey powered trip hammer probably provided no mechanical advantage to a slave with a sledgehammer.

The trip hammer was used for exactly the case you describe, pulverizing rocks to find gravel. The gravel could then be reduced in a furnace to extract valuable materials. This is historically how copper, tin, silver, and gold (along with rarer metals like antimony) were extracted and refined from ore.

As far as hardness goes; don't even worry about it. You can break up rocks using other rocks. Find a polish the hardest rock you can get, and use it as your hammer head. When it breaks, replace. In Roman times in the 4th century AD in Britain, there is an find of large iron hammer heads used for pounding ore.

The water-powered trip hammer is certainly in use in Han China by the first century BC. It is potentially in use in China several hundred years earlier, and there is sporadic evidence that it was used in the Roman empire from the 1st to 4th century AD. It returned to Europe in the 12th century where it achieved its widest use; and the mechanical principles behind its operation were crucial to the Industrial Revolution.

An alternative, used often in the Islamic world with limited access to waterpower, was the stamp mill, though this was not attested until the 10th century in Central Asia. However, creating a stamp mill is feasible with a Roman/Classical-era technology level.

Several possibilities:

• You could heat the silver, beat it into a thin plate, and then cut it into small pieces using scissors or a knife.


• You could probably use a file or iron or stone to grind the silver to dust, since silver is less hard than iron, not to mention stone.


• You could melt the silver and make it drip into water and collect the droplets.

Cupellation: https://en.m.wikipedia.org/wiki/Cupellation

Cupellation is the process of heating ores to separate noble metals (silver, gold, etc) from them. Silver is pretty reactive so finding silver by itself in nature is kind a hard so you are more likely to find it bonded with something like lead.

If your silver is still one solid chunk then all you need to do is heat it in a furnace and then cut or hammer it into smaller pieces. Or pour the molten silver into multiple canals that lead to multiple molds. Silver is a pretty easy metal to work with compared to iron and the Romans where already knowledgeable in iron working (Celts were better smiths however)

Smelting silver and silver working has been around since the bronze age so to someone with Roman tech smelting silver is a easy process. Heck the Romans where able to make alloys like pewter.