<blockquote>
  <p>...which allow for exposure of various rocks, still mountains are mostly grey/brown.</p>
</blockquote>

<p>The colourful minerals are apparent when you look up close. When you look from far away, the minerals are all mixed in your vision. My 2-year old daughter prepared a wonderful example of how this works:</p>

<p><a href="https://i.sstatic.net/iX4sd.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/iX4sd.jpg" alt="Colours"></a></p>

<p>Take a bunch of beautiful bright water colours, mix them together, and you end up having a greyish brown, dull colour.</p>

<p>Take another example. Sand, or sandstone. Boring yellow, white, or brown. But it's basically quartz. Finely divided quartz, unlike any of the beautiful quartz crystals you see for sale. Grain size is an important factor of the perception of colour.</p>

<hr>

<p>That said, one of the skills geology undergraduates learn in their first year of university, is distinguishing colours in a geological context. What to the untrained eye may seem brown or grey, appears like a world of colour. I still remember that when I just started my geology B.Sc about 10 years ago, we were given a bunch of rocks that all looked grey. After one year, they did not look grey any more. They were red-grey, brown-grey, <a href="https://www.google.com/search?tbm=isch&amp;q=blueschist&amp;tbs=imgo:1" rel="nofollow noreferrer">blue-grey</a>, <a href="https://www.google.com/search?tbm=isch&amp;q=greenschist&amp;tbs=imgo:1" rel="nofollow noreferrer">green-grey</a>, etc.</p>

<hr>

<p>Mountains can be coloured. Here are some pictures that I took myself a while ago:</p>

<p><a href="https://i.sstatic.net/KeduI.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/KeduI.jpg" alt="Ardon"></a></p>

<p><a href="https://i.sstatic.net/JNN1E.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/JNN1E.jpg" alt="Roded"></a></p>

<p>On a closer look I'm certain you will see that there are many colours in there: green, yellow, orange, pink, red, brown, white, black. No need for geological education to see that.</p>

<hr>

<blockquote>
  <p>Why isn't there a single mountain out of Olivine, Pyrite, Tourmaline
  or, say, Autunite, or any other brightly coloured rock?</p>
</blockquote>

<p>Most rocks are not composed of a single mineral. However, there are rocks composed only of olivine. They're call "dunites". Here's one:</p>

<p><a href="https://i.sstatic.net/YjiTM.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/YjiTM.jpg" alt="enter image description here"></a></p>

<p>See the rock behind? It's brown. That's because olivine contains ferrous iron. Once it's exposed to atmospheric oxygen, it becomes ferric iron. A better known name for ferric iron is "rust". This is generally the case for a lot of minerals. Colours commonly arise because of transition metals in a more reduced cationic state. Higher oxidation states are usually black, grey, red, and all kinds of earthy colours. The boring colours you see are commonly the result of "rusting" of rocks.</p>

<p>This is also the case for pyrite. It is an iron sulfide - shiny yellow. When exposed to the atmosphere, it rusts. In fact, patches of red soil in otherwise non-red soil are an indicator for a hidden ore deposit (<a href="https://en.wikipedia.org/wiki/Gossan" rel="nofollow noreferrer">gossan</a>).</p>

CC BY-SA 4.0
2021-07-23T17:03:37.757Z
A microscope can show the wide variety of colors in the crystals that make up many rocks, look at how the rainbow of colors in the crystals that make up Jacupirangite add up to a grey rock. http://www.alexstrekeisen.it/english/pluto/jacupirangite.php
John
CC BY-SA 4.0
2018-08-11T05:08:12.713Z
2018-08-11T05:08:12.713Z
Gimelist
<p>Color of mountains is due to rock composition and vegetation.
Very common rock colors are grey and brown for igneous, sedimentary and metamorphic rocks.  In higher elevations, predominant trees are conifers which are commonly dark greens. Also, by contrast with sky above, most mountains appear darker </p>

<p>There are colorful mountains though.</p>

<p>The Rainbow Mountains of China within the <a href="https://www.forbes.com/sites/trevornace/2016/03/02/rainbow-mountains-china-earths-paint-palette/" rel="nofollow noreferrer">Zhangye Danxia Landform Geological Park</a>.
<a href="https://i.sstatic.net/a6DHW.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/a6DHW.jpg" alt="enter image description here"></a>
<a href="https://i.sstatic.net/UWqxr.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/UWqxr.jpg" alt="enter image description here"></a></p>

<p><a href="http://www.garnetminetours.com/" rel="nofollow noreferrer">Gore mountain in New York</a> is not exclusively composed of garnet but is one of the largest garnet deposits on earth.
<a href="https://i.sstatic.net/koqlU.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/koqlU.jpg" alt="enter image description here"></a></p>

<p><a href="https://www.gamineral.org/ft/commercial/ftgravesmain.html" rel="nofollow noreferrer">Graves Mountain  in Georgia, USA</a> is largerly composed of aluminum silicates minerals like kyanite, sillimanie, and Pyrophyllite.
<a href="https://i.sstatic.net/kOebP.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/kOebP.jpg" alt="enter image description here"></a></p>

<p>Personally, I was amazed how much Mars and Titan looked like areas in the Mohave desert I have visited. </p>

CC BY-SA 4.0
2018-08-09T21:02:05.827Z
Thanks for your answer, first of all. Never heard about rainbow mountains before! But please elaborate on colour-rock relation. Statement `colours are grey and brown for igneous, sedimentary and metamorphic rocks` is way too vague IMO as there are essentially _no_ other rock types besides these three. Also, please clarify why those mentioned brightly coloured rocks are never found to form mountains. BTW you have mistyped one of the tags
PF4Public
CC BY-SA 4.0
2018-08-23T01:25:59.767Z
@PF4Public actually there are many more rock types, and continuums between these and the traditional three rock types. We just don't usually teach them to first year geology undergrads or the general undergrad because it introduces unnecessary complexity.
Gimelist
CC BY-SA 4.0
2019-06-23T20:50:11.603Z
Those rainbow mountains photographs seem heavily edited to show colours. In "normal" photos like those in https://commons.wikimedia.org/wiki/Category:Zhangye_National_Geopark those landscapes are still beautiful but in a more "rocky" colour.
Pere
CC BY-SA 4.0
2018-08-09T19:47:00.910Z
2018-08-10T10:13:28.043Z
2018-08-10T10:13:28.043Z
Earth Science Expatriate
<p>As Gary Kindel in his answer correctly said, mountains may consist of either magmatic, metamorphic or sedimentary rocks or all three together.</p>

<p>The greyish to brownish color is thus due to a mixture of all sorts of rocks and minerals that is covered by layers of eroded material of different grain sizes. This way, mountains appear to be of a single color when observed from a distance. This is similar to <a href="https://www.wikihow.com/Make-Gray" rel="nofollow noreferrer">mixing a couple of watercolors together</a> - the result will either be a greyish or a brown color. However, if we would magnify the watercolor mixture under a microscope, so that we see the individual pigments, we could tell that it isn't actually grey/brown. Same applies to the mountains. From a far, they appear to be grey/brown but when you get closer you can depict all sorts of colors.</p>

<p>The only exceptions to this are mountains, where the material is very well stratified, so that different colors can be seen from a distance.  </p>

<p>To answer your second question: Please note that Olivine, Pyrite and Tourmaline are not rocks but minerals. </p>

<p><strong>Olivine</strong> is mostly abundant in earth's mantle (check out <a href="https://en.wikipedia.org/wiki/Mohorovi%C4%8Di%C4%87_discontinuity" rel="nofollow noreferrer">Moho</a>). The chance that a mountain is build solely by a material from the mantle is highly unlikely. What happened to the material that was on top? Secondly, Olivine is not stable at earth's surface according to the Goldich dissolution series. It alters into clay minerals and iron oxides that are easily eroded by e.g. rainwater. Thus, if there was a mountain made of olivine it would have surely been eroded by now. </p>

<p><strong>Tourmaline</strong> is a mineral that forms in <a href="https://en.wikipedia.org/wiki/Pegmatite#Mineralogy" rel="nofollow noreferrer">pegmatites</a> and is thus far too rare to form an entire mountain. Especially since there is no process that individually picks Tourmalines from nature to build a mountain out of it.</p>

<p><strong>Pyrite</strong>; there is still a great debate in the literature about the formation processes of Pyrite. But it is most likely a mineral that forms in a secondary process due to the intrusion of hydrothermal mineral-rich water. Thus, Pyrite is not concentrated in one area and is, like Tourmaline, far too rare to form a mountain.</p>

CC BY-SA 4.0
2018-08-10T08:43:59.613Z
2018-08-10T08:43:59.613Z
Globoquadrina
<p>I want to contribute to the excellent answers already given pointing out two things:</p>
<ol>
<li>external color of a rock (altered) can be different from the rock minerals colours</li>
<li>the powder of a mineral can be of a different color of the mineral.. for example some metallic color sulphides of zinc have a red powder if scratched.</li>
</ol>

CC BY-SA 4.0
2021-07-22T17:34:28.660Z
2021-07-22T17:34:28.660Z
gino
<p>Observing many photos of mountains one can assume that most of the mountains are grey or brown. See also <a href="https://en.wikipedia.org/wiki/Mountain" rel="nofollow noreferrer">the mountain article</a> at Wikipedia.</p>

<p>There are however several ways <a href="https://en.wikipedia.org/wiki/Mountain_formation" rel="nofollow noreferrer">a mountain can form</a>, which allow for exposure of various rocks, still mountains are mostly grey/brown.</p>

<p>Why is it so? 
Why isn't there a single mountain out of <a href="https://en.wikipedia.org/wiki/Olivine" rel="nofollow noreferrer">Olivine</a>, <a href="https://en.wikipedia.org/wiki/Pyrite" rel="nofollow noreferrer">Pyrite</a>, <a href="https://en.wikipedia.org/wiki/Tourmaline" rel="nofollow noreferrer">Tourmaline</a> or, say, <a href="https://en.wikipedia.org/wiki/Autunite" rel="nofollow noreferrer">Autunite</a>, or any other brightly coloured rock?</p>

<geology><mountains><geomorphology>
Why are the mountains predominately grey or dark brown?
PF4Public
# Why are the mountains predominately grey or dark brown?

(Asked by: username_0 on 2018-08-09)

Observing many photos of mountains one can assume that most of the mountains are grey or brown. See also [the mountain article](https://en.wikipedia.org/wiki/Mountain) at Wikipedia.

There are however several ways [a mountain can form](https://en.wikipedia.org/wiki/Mountain_formation), which allow for exposure of various rocks, still mountains are mostly grey/brown.

Why is it so?
Why isn't there a single mountain out of [Olivine](https://en.wikipedia.org/wiki/Olivine), [Pyrite](https://en.wikipedia.org/wiki/Pyrite), [Tourmaline](https://en.wikipedia.org/wiki/Tourmaline) or, say, [Autunite](https://en.wikipedia.org/wiki/Autunite), or any other brightly coloured rock?

**Tags:** geology, mountains, geomorphology


---

## 4 answers

### Answer by username_1 on 2018-08-11. Score: 3 | Accepted answer

> ...which allow for exposure of various rocks, still mountains are mostly grey/brown.

The colourful minerals are apparent when you look up close. When you look from far away, the minerals are all mixed in your vision. My 2-year old daughter prepared a wonderful example of how this works:

[![Colours](https://i.sstatic.net/iX4sd.jpg)](https://i.sstatic.net/iX4sd.jpg)

Take a bunch of beautiful bright water colours, mix them together, and you end up having a greyish brown, dull colour.

Take another example. Sand, or sandstone. Boring yellow, white, or brown. But it's basically quartz. Finely divided quartz, unlike any of the beautiful quartz crystals you see for sale. Grain size is an important factor of the perception of colour.

---

That said, one of the skills geology undergraduates learn in their first year of university, is distinguishing colours in a geological context. What to the untrained eye may seem brown or grey, appears like a world of colour. I still remember that when I just started my geology B.Sc about 10 years ago, we were given a bunch of rocks that all looked grey. After one year, they did not look grey any more. They were red-grey, brown-grey, [blue-grey](https://www.google.com/search?tbm=isch&q=blueschist&tbs=imgo:1), [green-grey](https://www.google.com/search?tbm=isch&q=greenschist&tbs=imgo:1), etc.

---

Mountains can be coloured. Here are some pictures that I took myself a while ago:

[![Ardon](https://i.sstatic.net/KeduI.jpg)](https://i.sstatic.net/KeduI.jpg)

[![Roded](https://i.sstatic.net/JNN1E.jpg)](https://i.sstatic.net/JNN1E.jpg)

On a closer look I'm certain you will see that there are many colours in there: green, yellow, orange, pink, red, brown, white, black. No need for geological education to see that.

---

> Why isn't there a single mountain out of Olivine, Pyrite, Tourmaline
> or, say, Autunite, or any other brightly coloured rock?

Most rocks are not composed of a single mineral. However, there are rocks composed only of olivine. They're call "dunites". Here's one:

[![enter image description here](https://i.sstatic.net/YjiTM.jpg)](https://i.sstatic.net/YjiTM.jpg)

See the rock behind? It's brown. That's because olivine contains ferrous iron. Once it's exposed to atmospheric oxygen, it becomes ferric iron. A better known name for ferric iron is "rust". This is generally the case for a lot of minerals. Colours commonly arise because of transition metals in a more reduced cationic state. Higher oxidation states are usually black, grey, red, and all kinds of earthy colours. The boring colours you see are commonly the result of "rusting" of rocks.

This is also the case for pyrite. It is an iron sulfide - shiny yellow. When exposed to the atmosphere, it rusts. In fact, patches of red soil in otherwise non-red soil are an indicator for a hidden ore deposit ([gossan](https://en.wikipedia.org/wiki/Gossan)).

> **Comments:**
> **username_2**: A microscope can show the wide variety of colors in the crystals that make up many rocks, look at how the rainbow of colors in the crystals that make up Jacupirangite add up to a grey rock. http://www.alexstrekeisen.it/english/pluto/jacupirangite.php  

---

### Answer by username_3 on 2018-08-09. Score: 3

Color of mountains is due to rock composition and vegetation.
Very common rock colors are grey and brown for igneous, sedimentary and metamorphic rocks. In higher elevations, predominant trees are conifers which are commonly dark greens. Also, by contrast with sky above, most mountains appear darker

There are colorful mountains though.

The Rainbow Mountains of China within the [Zhangye Danxia Landform Geological Park](https://www.forbes.com/sites/trevornace/2016/03/02/rainbow-mountains-china-earths-paint-palette/).
[![enter image description here](https://i.sstatic.net/a6DHW.jpg)](https://i.sstatic.net/a6DHW.jpg)
[![enter image description here](https://i.sstatic.net/UWqxr.jpg)](https://i.sstatic.net/UWqxr.jpg)

[Gore mountain in New York](http://www.garnetminetours.com/) is not exclusively composed of garnet but is one of the largest garnet deposits on username_3.
[![enter image description here](https://i.sstatic.net/koqlU.jpg)](https://i.sstatic.net/koqlU.jpg)

[Graves Mountain in Georgia, USA](https://www.gamineral.org/ft/commercial/ftgravesmain.html) is largerly composed of aluminum silicates minerals like kyanite, sillimanie, and Pyrophyllite.
[![enter image description here](https://i.sstatic.net/kOebP.jpg)](https://i.sstatic.net/kOebP.jpg)

Personally, I was amazed how much Mars and Titan looked like areas in the Mohave desert I have visited.

> **Comments:**
> **username_0**: Thanks for your answer, first of all. Never heard about rainbow mountains before! But please elaborate on colour-rock relation. Statement `colours are grey and brown for igneous, sedimentary and metamorphic rocks` is way too vague IMO as there are essentially _no_ other rock types besides these three. Also, please clarify why those mentioned brightly coloured rocks are never found to form mountains. BTW you have mistyped one of the tags  
> **username_1**: @username_0 actually there are many more rock types, and continuums between these and the traditional three rock types. We just don't usually teach them to first year geology undergrads or the general undergrad because it introduces unnecessary complexity.  
> **username_4**: Those rainbow mountains photographs seem heavily edited to show colours. In "normal" photos like those in https://commons.wikimedia.org/wiki/Category:Zhangye_National_Geopark those landscapes are still beautiful but in a more "rocky" colour.  

---

### Answer by username_5 on 2018-08-10. Score: 3

As Gary Kindel in his answer correctly said, mountains may consist of either magmatic, metamorphic or sedimentary rocks or all three together.

The greyish to brownish color is thus due to a mixture of all sorts of rocks and minerals that is covered by layers of eroded material of different grain sizes. This way, mountains appear to be of a single color when observed from a distance. This is similar to [mixing a couple of watercolors together](https://www.wikihow.com/Make-Gray) - the result will either be a greyish or a brown color. However, if we would magnify the watercolor mixture under a microscope, so that we see the individual pigments, we could tell that it isn't actually grey/brown. Same applies to the mountains. From a far, they appear to be grey/brown but when you get closer you can depict all sorts of colors.

The only exceptions to this are mountains, where the material is very well stratified, so that different colors can be seen from a distance.

To answer your second question: Please note that Olivine, Pyrite and Tourmaline are not rocks but minerals.

**Olivine** is mostly abundant in username_3's mantle (check out [Moho](https://en.wikipedia.org/wiki/Mohorovi%C4%8Di%C4%87_discontinuity)). The chance that a mountain is build solely by a material from the mantle is highly unlikely. What happened to the material that was on top? Secondly, Olivine is not stable at username_3's surface according to the Goldich dissolution series. It alters into clay minerals and iron oxides that are easily eroded by e.g. rainwater. Thus, if there was a mountain made of olivine it would have surely been eroded by now.

**Tourmaline** is a mineral that forms in [pegmatites](https://en.wikipedia.org/wiki/Pegmatite#Mineralogy) and is thus far too rare to form an entire mountain. Especially since there is no process that individually picks Tourmalines from nature to build a mountain out of it.

**Pyrite**; there is still a great debate in the literature about the formation processes of Pyrite. But it is most likely a mineral that forms in a secondary process due to the intrusion of hydrothermal mineral-rich water. Thus, Pyrite is not concentrated in one area and is, like Tourmaline, far too rare to form a mountain.


---

### Answer by username_6 on 2021-07-22. Score: 0

I want to contribute to the excellent answers already given pointing out two things:

1. external color of a rock (altered) can be different from the rock minerals colours
2. the powder of a mineral can be of a different color of the mineral.. for example some metallic color sulphides of zinc have a red powder if scratched.


---

