# Why are most elemental metals grey?

**URL:** <https://boards.straightdope.com/t/why-are-most-elemental-metals-grey/671763>\
**Category:** Factual Questions\
**Created:** [October 20, 2013, 11:32pm UTC](https://boards.straightdope.com/t/why-are-most-elemental-metals-grey/671763 "2013-10-20T23:32:12Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![RickJay](https://avatars.discourse-cdn.com/v4/letter/r/bb73d2/32.png) [@RickJay](https://boards.straightdope.com/u/RickJay)\
**Post date:** [October 20, 2013, 11:32pm UTC](https://boards.straightdope.com/t/why-are-most-elemental-metals-grey/671763/1 "2013-10-20T23:32:12Z")

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With a few exceptions, like gold and copper, most elemental metals are basically just gray. Some are shinier than others - silver is shinier than iron - but for the most part they’re all gray. Except for gold and copper, and maybe another one or two I don’t recall. They’re gray if they’re light (Lithium) and gray if they’re really heavy (Bismuth.)

Why is that? And what’s special about gold and copper?

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**Author:** ![ouryL](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ouryl/32/6067_2.png) [@ouryL](https://boards.straightdope.com/u/ouryL)\
**Post date:** [October 20, 2013, 11:58pm UTC](https://boards.straightdope.com/t/why-are-most-elemental-metals-grey/671763/2 "2013-10-20T23:58:29Z")

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[causesofcolor](http://www.webexhibits.org/causesofcolor/9.html)

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**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\
**Post date:** [October 21, 2013, 2:50am UTC](https://boards.straightdope.com/t/why-are-most-elemental-metals-grey/671763/3 "2013-10-21T02:50:12Z")

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That is a nice article, **ouryL** , but one thing it does not seem to mention is that a clean, smooth copper surface is actually light pink, not at all a normal ‘metally’ sort of color. The distinctive copper color we are used to is due to a thin coating of oxide which quite rapidly forms on the exposed metallic surface, but you can see the pink by, for instance, dipping the copper in a suitable acid that will dissolve the oxide off, temporarily.

I am not sure whether the oxide that forms is cuprous (Cu[sub]2[/sub]O) or cupric (CuO), or maybe a mixture of the two. In powder form, cuprous oxide is yellow or red, and cupric oxide is black, but that may not tell you much about what they would look like in a thin surface layer with pink metal behind them.

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**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\
**Post date:** [October 21, 2013, 3:02am UTC](https://boards.straightdope.com/t/why-are-most-elemental-metals-grey/671763/4 "2013-10-21T03:02:32Z")

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> [@RickJay](#):
>
> With a few exceptions, like gold and copper, most elemental metals are basically just gray. Some are shinier than others - silver is shinier than iron - but for the most part they’re all gray. Except for gold and copper, and maybe another one or two I don’t recall. They’re gray if they’re light (Lithium) and gray if they’re really heavy (Bismuth.)
> 
> Why is that? And what’s special about gold and copper?

The metals have the free outer electrons. The metallic bonding doesn’t lock them up. Turns out that these electrons are then able to reflect all the visible frequencies and have no particular absorption spectrum (colour)…Because the electrons are free to jump to any energy the visible spectrum would have them jump to. Anyway they reflect … which is far more difficult to explain .(its perhaps only possible to say ‘these free electrons are obviously the cause metals are reflective…’)

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**Author:** ![the\_diego](https://avatars.discourse-cdn.com/v4/letter/t/7bcc69/32.png) [@the\_diego](https://boards.straightdope.com/u/the_diego)\
**Post date:** [October 21, 2013, 6:04am UTC](https://boards.straightdope.com/t/why-are-most-elemental-metals-grey/671763/5 "2013-10-21T06:04:57Z")

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The above post explains why they are colorless. They are often grey when the surface is coated by oxides that are usually dark.

And it’s not just pure metals. A lot of metal oxides and sulfides found as natural minerals can have a metallic luster and most of them are dark grey.