In a fantasy setting with 15th century metallurgy, what metals could have been refined that were not discovered in our own medieval period?

Question

For the fantasy setting I'm working on, for a roleplaying game system, civilizations have stagnated into a 15th century technology and metallurgy level with some deviations to make for more interesting gameplay or story.

One thing I am trying to do is make a list of materials available within the setting so I know what can, and can't, be made. I'm also using this to give myself a rough idea of how items made from one material would compare to similar items made from another material.

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In a previous question, someone showed me a useful chart on Wikipedia showing which metals were discovered when. I'm curious about what metals could have been refined using the techniques and knowledge of the 15th century if they simply had access to, and knew about, the ores needed to refine said metals.

I am also curious about metals that could be made possible with 15th century alchemy/chemistry knowledge to separate unwanted materials from ore to produce something that can be refined in a traditional smelting furnace, even if such a process is time consuming and expensive.

For this question, we're ignoring magic. There are materials that can only be magically obtained, but we're not discussing them in this question.

Answer 1

Specific examples

• Platinum can be found in native form; so that they could have had platinum in the 1400s if only they had access to native platinum deposits. In real history, platinum was not known to European chemists before the 18th century because there are no significant native platinum deposits in Europe; but there are such deposits in the Americas.

• Cobalt can be extracted from ore using reduction with carbon in a blast furnace. In real history cobalt was discovered in the 18th century, but a very lucky alchemist could have obtained it in the 15th.

• Nickel, molybdenum and manganese should have been available in the 15th century, but weren't, to the eternal shame of European alchemists. There is nothing special about smelting nickel, molybdenum or manganese; they could have done it, but they didn't, and the world had to wait for the 18th century.

• Metallic chromium can be smelted from the oxide by heating with charcoal, so that it could have been available in the 15th century if only the alchemists had access to crocoite.

• Sodium, potassium and aluminum metals cannot be smelted without electrochemistry. (OK, aluminum can be extracted without electrochemistry provided one has access to metallic potassium; which doesn't help.)

• Extracting magnesium in metallic form requires either very high temperatures or electrochemistry, both of which were utterly unavailable to 15th century alchemists.

• Barium and calcium are highly reactive metals, and I'm afraid that obtaining them in metallic form is way beyond the abilities of 15th century alchemists. (Note that the Wikipedia table mentioned in the question lists the date when their existence was first proven, not the date when they were first obtained in metallic form, which was much later.)

General considerations

• Before modern chemistry, a metal had a chance of being known in its metallic form only if it was found in its native state, or if it could be smelted from its oxide (or sulfide) using carbon (or carbon monoxide). No other smelting method was available.

  Look at the chemical reactivity series. Metals more reactive than titanium cannot be smelted from oxides using carbon, so that there is no way for them to be available in metallic form before modern chemistry.

• Before the middle of the 17th century chemistry was almost purely qualitative. Chemists used very very little quantitative measurements; there was no such thing as a temperature scale, a density scale, a hardness scale and so on. Two substances were recognized as being different only if they very conspicuously different using purely qualitative observations.

  An example: it is not hard to smelt molybdenum once you know that molybdena is neither graphite nor galena. But how could they know that molybdena is not graphite? It looks like graphite. It leaves a dark mark on paper like graphite. It can be used as a solid lubricant like graphite. It was actually used interchangeably with graphite, and nobody noticed anything out of the ordinary. (Fun factoid: those three substances were not really distinguished before the modern age. They thought that graphite was some sort of lead ore; that's why we speak of the "lead" of a pencil. No, pencils never contained the metal lead.)

• Before the second half of the 17th century chemistry had no theoretical basis whatsoever. (And the theoretical basis developed in the second half of the 17th century was fundamentally wrong anyway.) This is critical: in the absence of a theoretical basis chemists had no idea how to organize their knowledge. All chemical knowledge was an unsorted, unordered, chaotic mass of anecdotes. It is very hard to make progress when your field of study consists of myriads of anecdotes, with no stable quantitative measurements, with no ordering principles, with no commonly agreed terminology.

• Indeed, because chemistry was a chaotic collection of purely qualitative anecdotes, it is sometimes hard to say exactly was counts as a metal being available. For example, there are Ancient Egyptian artifacts which contain a (natural) alloy of gold with small amounts of platinum; but we don't consider platinum being available before the modern age, because the Ancient Egyptians themselves were not aware that there was anything amiss with their gold. Some samples of Indian Wootz steel (imported in Europe as "Damascus" steel, because it came through Damascus and the Europeans had no idea where it ultimately came from) contain some small amounts of vanadium; but nobody knew what was that made that "iron" so desirable.

Answer 2

I think there are two main methods for refining. Heat, and Electricity. Both of these could be produced magically and allow metallurgical development more easily.

For heat, the issue is that you often need a lot more heat than can be developed through a wood or charcoal fire. Like 4000°F instead of 2000°F. Magical flame could allow you to smelt and work these metals.

Some metals need less heat. Zinc for instance will evaporate in a charcoal fire. So the control of the temperature is what is really important.

Another means of smelting is electrolytically, for instance of Aluminium. Magically produced electrical power could do this.

In both cases, we are probably talking about small batches (grams to ounces), but it could be a small batch every day.

(I actually first considered this when I got introduced to the Runequest roll playing system. Everyone could have some magic, so why not the local blacksmith?)