<p>The eutectic is the minimum melting point of a mixed material, like soda lime glass made from sodium hydroxide, calcium oxide, and silicon dioxide. That mixture, in the proper proportions, lowers the melting point of quartz sand (silicon dioxide) from 1700 to under 1000 Celsius. In the mantle the mixture is far more complex but if I remember my geochemistry Aluminium, Iron, Magnesium, and Calcium are the main elements that lower the melting point of pure silica in magmatic melts. Water can be very important as it not only lowers the melting point of saturated rocks but also carries heat into lower temperature melting materials, especially in subduction zones.</p>

CC BY-SA 4.0
2018-05-20T14:45:21.270Z
2018-05-20T14:45:21.270Z
Ash
<p>Start with my answer to this very highly related question here:</p>

<p><a href="https://earthscience.stackexchange.com/a/2742/725">https://earthscience.stackexchange.com/a/2742/725</a></p>

<hr>

<p>The melting point of minerals in isolation, or a pure substance is higher than mixtures of minerals. For example - a (well-mixed) mixture of quartz and pyroxene will melt at a lower temperature than pure quartz or pure pyroxene. The exact temperature is dependent on the proportions.</p>

<p>In general, the more different kind of components (i.e. "things": minerals, elements, molecules, etc) you add to a mixture, the lower the melting point of the mixture as a whole.</p>

<p>For example, sea water melts at -2 °C because it's a mixture of water (melts at 0 °C) and all kinds of salts. Steel melts at a lower temperature than pure iron because it's a mixture of iron and carbon.</p>

CC BY-SA 4.0
2018-05-20T19:54:09.460Z
It's also possible that some components of a mixture might dissolve in the first to become liquid, rather than melt themselves.  For example, you can dissolve quite a bit of common salt (among many other things) in water, even though the water is nowhere near the salt's 801 C metlting point.
jamesqf
CC BY-SA 4.0
2018-05-20T21:29:30.690Z
i see... So Bowen's reaction series depends on composition of magma and not just the individual minerals in isolation. That's why it's a purely experimental result.
Neeraj Kulkarni
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2018-05-20T23:22:22.403Z
@NeerajKulkarni exactly. It's an experimental result that has strong relevance for natural systems. Bowen's experiments were conducted about 100 years ago, so they miss a lot of complexities that exist in natural rocks. But, they are generally applicable for most eruptive rocks (such as basalt, andesite and rhyolite).
Gimelist
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2018-05-21T08:09:03.763Z
@NeerajKulkarni It's not purely an experimental result. You can predict the order of mineral crystallization from thermodynamics as well.
bon
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2018-05-21T09:01:26.180Z
@bon sorry to nitpick, but thermodynamic data used to make these predictions is obtained using experiments.
Gimelist
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2018-05-21T15:05:09.447Z
@Michael Well yes that's true :P. But you need a theoretical framework to use the data within as well.
bon
CC BY-SA 4.0
2018-05-20T11:36:45.570Z
2018-05-20T11:36:45.570Z
Gimelist
<p>Looking at this website, I can see the melting point of the following minerals: <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/Geophys/meltrock.html" rel="nofollow noreferrer">http://hyperphysics.phy-astr.gsu.edu/hbase/Geophys/meltrock.html</a></p>

<p>Apparently at a temperature of 1200 °C, all the minerals exist in a molten state. But, looking at the melting point for <a href="https://en.wikipedia.org/wiki/Quartz" rel="nofollow noreferrer">quartz</a> on Wikipedia I find that the melting point is close to 1700 °C. What’s going on here?</p>

<p>It can’t be an effect of the pressure. In the interior, the pressure will be higher and thus further increase the melting point. </p>

CC BY-SA 4.0
2018-05-20T19:15:54.057Z
It is wrong, maybe they meant to say "all magmas" ?
blacksmith37
<geochemistry><mineralogy><minerals>
Melting point of minerals
Neeraj Kulkarni
# Melting point of minerals

(Asked by: username_0 on 2018-05-19)

Looking at this website, I can see the melting point of the following minerals: <http://hyperphysics.phy-astr.gsu.edu/hbase/Geophys/meltrock.html>

Apparently at a temperature of 1200 °C, all the minerals exist in a molten state. But, looking at the melting point for [quartz](https://en.wikipedia.org/wiki/Quartz) on Wikipedia I find that the melting point is close to 1700 °C. What’s going on here?

It can’t be an effect of the pressure. In the interior, the pressure will be higher and thus further increase the melting point.

**Tags:** geochemistry, mineralogy, minerals

> **Comments:**
> **username_1**: It is wrong, maybe they meant to say "all magmas" ?  

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## 2 answers

### Answer by username_3 on 2018-05-20. Score: 6 | Accepted answer

Start with my answer to this very highly related question here:

<https://earthscience.stackexchange.com/a/2742/725>

---

The melting point of minerals in isolation, or a pure substance is higher than mixtures of minerals. For example - a (well-mixed) mixture of quartz and pyroxene will melt at a lower temperature than pure quartz or pure pyroxene. The exact temperature is dependent on the proportions.

In general, the more different kind of components (i.e. "things": minerals, elements, molecules, etc) you add to a mixture, the lower the melting point of the mixture as a whole.

For example, sea water melts at -2 °C because it's a mixture of water (melts at 0 °C) and all kinds of salts. Steel melts at a lower temperature than pure iron because it's a mixture of iron and carbon.

> **Comments:**
> **username_4**: It's also possible that some components of a mixture might dissolve in the first to become liquid, rather than melt themselves.  For example, you can dissolve quite a bit of common salt (among many other things) in water, even though the water is nowhere near the salt's 801 C metlting point.  
> **username_0**: i see... So Bowen's reaction series depends on composition of magma and not just the individual minerals in isolation. That's why it's a purely experimental result.  
> **username_3**: @username_0 exactly. It's an experimental result that has strong relevance for natural systems. Bowen's experiments were conducted about 100 years ago, so they miss a lot of complexities that exist in natural rocks. But, they are generally applicable for most eruptive rocks (such as basalt, andesite and rhyolite).  
> **username_5**: @username_0 It's not purely an experimental result. You can predict the order of mineral crystallization from thermodynamics as well.  
> **username_3**: @username_5 sorry to nitpick, but thermodynamic data used to make these predictions is obtained using experiments.  
> **username_5**: @Michael Well yes that's true :P. But you need a theoretical framework to use the data within as well.  

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### Answer by username_2 on 2018-05-20. Score: 1

The eutectic is the minimum melting point of a mixed material, like soda lime glass made from sodium hydroxide, calcium oxide, and silicon dioxide. That mixture, in the proper proportions, lowers the melting point of quartz sand (silicon dioxide) from 1700 to under 1000 Celsius. In the mantle the mixture is far more complex but if I remember my geochemistry Aluminium, Iron, Magnesium, and Calcium are the main elements that lower the melting point of pure silica in magmatic melts. Water can be very important as it not only lowers the melting point of saturated rocks but also carries heat into lower temperature melting materials, especially in subduction zones.


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