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I know that glass is actually green in that mirrors will always leave a green tint. This is because, although it's a small margin, green is the most absorbed wavelength for glass. Following on from this, what colour would I expect each transition metal to be (i.e which colour light do they reflect each).

Side note: For simplicity, I'm asking for a comprehensive list, but I'm happy to accept a more generalised answer if possible.

yolo
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    They are all variations on silver-grey, pretty much like just about all metals (except gold and copper that absorb a bit more on the blue end than most). – Jon Custer Feb 03 '22 at 20:57
  • @jon custer. But Silver is a mixture of wavelengths. Which is it's peak? – yolo Feb 03 '22 at 21:47
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    Re, "...glass is actually green..." Soda-lime glass usually is green, or sometimes, greenish blue; but there are other recipes for glass, and many of those are colorless. You tend to see a lot of soda-lime glass because it can be worked at a lower temperature than other formulas, which makes the cost of manufacturing things from it significantly less than the cost for other types of glass. – Solomon Slow Feb 03 '22 at 23:03
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    Possible duplicates: https://physics.stackexchange.com/q/72368/2451 and links therein. – Qmechanic Feb 04 '22 at 02:13
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    @SolomonSlow, pure soda-lime class is colorless. the green tint comes from iron oxide, a common impurity. Changing the oxidation state of the iron will yield brown instead of green. – niels nielsen Feb 04 '22 at 07:50

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You can look at the reflectance curves of the metal in the 380-750 nm range. In white light it will be "colored" by the wavelengths that are strongly reflected. In practice this is a slight coloration for most metals, but you could imagine an analog of looking along the mirror glass where you look at light reflected multiple times through a tube of the metal.

Here is an example set of curves from PV Lighthouse:

Copper is the most obvious colored metal, reflecting more yellow and red light than blue, producing the copper tone. Chromium on the other hand is (slightly) bluish, while molybdenum is a bit "greener" and tin nearly "white".

In practice the surface matters a lot. Oxides and surface finish can change the color strongly. Because of the Fresnel equations, reflectance can in principle be polarization- and angle-dependent, especially if the refractive index changes a lot with wavelength. This is not the case for metals as far as I know, so the contribution is minimal, but some of the dielectric oxide layers this can matter (not to mention when the layer itself has thin-film color).

So the general answer is that perfectly pure metals usually have very weak color, but it exists. In practice it is more the surface that determines what they look like. Pure cobalt and samarium are much more silvery than my cubes below, due to oxidation.

Some elements as 1 cm cubes

Anders Sandberg
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