<p>As often in geology of any scale, the surface is only a manifestation of a 3-dimensional body. </p>

<p>It's typical for igneous rocks (e.g. granite see <a href="http://www.oldearth.org/curriculum/geology/images/Rapakivigranite_ss.jpg" rel="nofollow">here</a>) that the polished surface have the <a href="https://en.wikipedia.org/wiki/Voronoi_diagram" rel="nofollow">Voronoi</a>-like-pattern. The minerals grow from a nucleus until they reach the next crystal and the melt is finished. Every point in the rock can be related back to its closest crystal nucleus, depending on the solidus conditions for the chemical composition.</p>

<p>Check this short <a href="https://www.youtube.com/watch?v=tLGBa4tkiJI" rel="nofollow">animation</a>.</p>

<p>You can see the same pattern in the microstructure of metals, e.g. ferrite and pearlite in steel <a href="https://www.researchgate.net/profile/Wang_Youde/publication/279457723/figure/fig1/AS:294271627350019@1447171231870/Fig-1-Microstructure-of-Q235-steel-material-White-part-is-ferrite-and-black-part-is.png" rel="nofollow">e.g. here</a>. </p>

CC BY-SA 3.0
2016-08-09T10:04:20.217Z
2016-08-09T10:04:20.217Z
user2821
<p>What is this pattern in the samples' surface called and how/why is it formed? I remember having seen a similar pattern in galvanized sheets. </p>

<p>Photos of metal samples from Wikimedia Commons (<a href="https://commons.m.wikimedia.org/wiki/File:Vanadium-bar.jpg" rel="nofollow noreferrer">here</a> and <a href="https://commons.m.wikimedia.org/wiki/File:Aluminium_etched.jpg" rel="nofollow noreferrer">here</a>):</p>

<p><a href="https://i.sstatic.net/ubAnR.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/ubAnR.jpg" alt="Vanadium bar"></a>
<a href="https://i.sstatic.net/x3RXR.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/x3RXR.jpg" alt="Aluminum ingot"></a></p>

CC BY-SA 3.0
2016-06-19T08:40:00.380Z
Not related to Earth Science, more likely chemistry or physics. However, these things are called "crystallites". I would start with the [Wikipedia article](https://en.wikipedia.org/wiki/Crystallite) about the subject.
Gimelist
<geochemistry><mineralogy><crystallography>
Voronoi-like pattern in metal samples
amyspark
# Voronoi-like pattern in metal samples

(Asked by: username_0 on 2016-06-19)

What is this pattern in the samples' surface called and how/why is it formed? I remember having seen a similar pattern in galvanized sheets.

Photos of metal samples from Wikimedia Commons ([here](https://commons.m.wikimedia.org/wiki/File:Vanadium-bar.jpg) and [here](https://commons.m.wikimedia.org/wiki/File:Aluminium_etched.jpg)):

[![Vanadium bar](https://i.sstatic.net/ubAnR.jpg)](https://i.sstatic.net/ubAnR.jpg)
[![Aluminum ingot](https://i.sstatic.net/x3RXR.jpg)](https://i.sstatic.net/x3RXR.jpg)

**Tags:** geochemistry, mineralogy, crystallography

> **Comments:**
> **username_1**: Not related to Earth Science, more likely chemistry or physics. However, these things are called "crystallites". I would start with the [Wikipedia article](https://en.wikipedia.org/wiki/Crystallite) about the subject.  

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## 1 answers

### Answer by username_2 on 2016-08-09. Score: 2 | Accepted answer

As often in geology of any scale, the surface is only a manifestation of a 3-dimensional body.

It's typical for igneous rocks (e.g. granite see [here](http://www.oldearth.org/curriculum/geology/images/Rapakivigranite_ss.jpg)) that the polished surface have the [Voronoi](https://en.wikipedia.org/wiki/Voronoi_diagram)-like-pattern. The minerals grow from a nucleus until they reach the next crystal and the melt is finished. Every point in the rock can be related back to its closest crystal nucleus, depending on the solidus conditions for the chemical composition.

Check this short [animation](https://www.youtube.com/watch?v=tLGBa4tkiJI).

You can see the same pattern in the microstructure of metals, e.g. ferrite and pearlite in steel [e.g. here](https://www.researchgate.net/profile/Wang_Youde/publication/279457723/figure/fig1/AS:294271627350019@1447171231870/Fig-1-Microstructure-of-Q235-steel-material-White-part-is-ferrite-and-black-part-is.png).


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