<p>Melting lunar dust of basaltic composition will result (unsurprisingly) in basalt lava. There might be some volatile loss - if for some reason the basalt had some H<sub>2</sub>O or CO<sub>2</sub> trapped in the solid you will most likely lose it. It's probably not going to change its chemical properties much though.</p>

<p>On Earth, as lava cools down fast, for example when it's erupted underwater, or when it's the top of a lava flow in contact with air, it quenches to volcanic glass. When it cools down slower, there is enough time for small crystalline material to form in it. These are usually tiny crystals in the μm size. On the Moon, I reckon the lava would cool down slightly slower than on Earth (since there is no air to conduct away heat), but since you're talking about a lava layer which is only 2 cm thick I'm pretty sure it will cool down fast enough for the formation of glass, and any crystalline portion of it will be negligible. I am not sure whether it will crack or not. From my own experience of melting rocks, when you have a similar amount cooling down in Earth's atmosphere, they crack. But then, silicate glass does not crack when cooled down in air. I guess it comes down to the composition of the rock/glass.</p>

<p>The lava will not percolate down to the regolith. Lavas hardly penetrate soils on Earth, so it is probably not going to happen on the Moon where the gravity is much weaker.</p>

<p>If I were looking for construction materials on the Moon, I would just build a quarry. Seems easier than melting down dust.</p>

CC BY-SA 3.0
2016-07-26T14:06:12.433Z
The regolith on the Moon is between 10 and 30 m deep, and on the very edge of a crater such as proposed, it is deeper as the surface has been folded back on itself by the impact blast. A quarry at the very beginning seems difficult, but there are plenty of large boulders. I don't know how hard it would be to cut them into precise shapes, i'll have to look into it.
kim holder
CC BY-SA 3.0
2016-07-27T10:40:24.823Z
@kimholder As hard as cutting basalt glass sheets into shapes? I guess that's one of the reasons we don't have colonies on the moon yet.
Gimelist
CC BY-SA 3.0
2016-07-27T13:23:10.940Z
I had thought the cutting could be done just before the sheet froze. And the sheet can be melted into specific shapes in the first place.
kim holder
CC BY-SA 3.0
2016-07-26T10:09:27.633Z
2016-07-26T10:09:27.633Z
Gimelist
<p>The idea is to melt the fine-grain portion of basalt regolith using a large Fresnel lens, and let it cool to a solid. The lens would track along a tamped bed of material leaving a molten puddle something like 2 cm thick. This would be done on top of more regolith with the same characteristics - which means some of the material would sink into the stuff below and get mixed. Then it is left to cool to a solid.</p>

<p>The conjecture is that Fresnel lenses, and the equipment needed to create flat beds of tamped powder regolith and track such lenses across it, is so light that it could be a good way of creating construction materials. If they aren't very good materials they could make up for that in the simplicity of making them and the possibility of making enough that the fact they have weaknesses doesn't matter - just use more.</p>

<p>What might the material yielded by such a process be like?</p>

<p><hr>
Edit: Since someone asked, this could yield thin basalt objects of any 2D shape, or objects built up of various layers into 3D shapes. Such objects can be joined with more molten basalt and parged to form continuous rock walls, floors, and arches. An approach to excavation also based largely on the use of lenses (for trenching, and boring for the placement of explosive micro-charges) is used to create voids that are then lined with rock this way.</p>

<p>It is explained more <a href="http://moonwards.com/index.html#sketchfab" rel="nofollow noreferrer">here</a>, and here is the current model of the equipment:</p>

<p><a href="https://i.sstatic.net/MKLrF.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/MKLrF.jpg" alt="Lunar Melt in place bed with lenses"></a></p>

CC BY-SA 3.0
2016-07-05T20:31:09.840Z
@Phiteros This is here because the conditions on the surface of the Moon are sufficiently different to change the results compared to Earth. If it goes unanswered i might move it to [earthscience.se] but the best answers would come from experienced planetary scientists. Would it cool into a glass or have a crystal structure? Would it sink far into the underlying grains and be full of inclusions? Will it crack as it cools?
kim holder
CC BY-SA 3.0
2016-07-05T23:11:34.910Z
@SF presently i'll edit this to be more clear. For an initial mission, i think the scanning technique is more feasible.
kim holder
CC BY-SA 3.0
2016-07-06T15:59:19.523Z
@Phiteros regolith conducts heat very poorly, and the bed would contain only the particles less than 3mm wide. That assessment sounds reasonable.
kim holder
<geochemistry><planetary-science><moon><magmatism>
Melting basalt on the lunar surface - what would the resulting material be like?
kim holder
# Melting basalt on the lunar surface - what would the resulting material be like?

(Asked by: username_0 on 2016-07-04)

The idea is to melt the fine-grain portion of basalt regolith using a large Fresnel lens, and let it cool to a solid. The lens would track along a tamped bed of material leaving a molten puddle something like 2 cm thick. This would be done on top of more regolith with the same characteristics - which means some of the material would sink into the stuff below and get mixed. Then it is left to cool to a solid.

The conjecture is that Fresnel lenses, and the equipment needed to create flat beds of tamped powder regolith and track such lenses across it, is so light that it could be a good way of creating construction materials. If they aren't very good materials they could make up for that in the simplicity of making them and the possibility of making enough that the fact they have weaknesses doesn't matter - just use more.

What might the material yielded by such a process be like?

---

Edit: Since someone asked, this could yield thin basalt objects of any 2D shape, or objects built up of various layers into 3D shapes. Such objects can be joined with more molten basalt and parged to form continuous rock walls, floors, and arches. An approach to excavation also based largely on the use of lenses (for trenching, and boring for the placement of explosive micro-charges) is used to create voids that are then lined with rock this way.

It is explained more [here](http://moonwards.com/index.html#sketchfab), and here is the current model of the equipment:

[![Lunar Melt in place bed with lenses](https://i.sstatic.net/MKLrF.jpg)](https://i.sstatic.net/MKLrF.jpg)

**Tags:** geochemistry, planetary-science, moon, magmatism

> **Comments:**
> **username_0**: @Phiteros This is here because the conditions on the surface of the Moon are sufficiently different to change the results compared to Earth. If it goes unanswered i might move it to [earthscience.se] but the best answers would come from experienced planetary scientists. Would it cool into a glass or have a crystal structure? Would it sink far into the underlying grains and be full of inclusions? Will it crack as it cools?  
> **username_0**: @SF presently i'll edit this to be more clear. For an initial mission, i think the scanning technique is more feasible.  
> **username_0**: @Phiteros regolith conducts heat very poorly, and the bed would contain only the particles less than 3mm wide. That assessment sounds reasonable.  

---

## 1 answers

### Answer by username_1 on 2016-07-26. Score: 3

Melting lunar dust of basaltic composition will result (unsurprisingly) in basalt lava. There might be some volatile loss - if for some reason the basalt had some H2O or CO2 trapped in the solid you will most likely lose it. It's probably not going to change its chemical properties much though.

On Earth, as lava cools down fast, for example when it's erupted underwater, or when it's the top of a lava flow in contact with air, it quenches to volcanic glass. When it cools down slower, there is enough time for small crystalline material to form in it. These are usually tiny crystals in the μm size. On the Moon, I reckon the lava would cool down slightly slower than on Earth (since there is no air to conduct away heat), but since you're talking about a lava layer which is only 2 cm thick I'm pretty sure it will cool down fast enough for the formation of glass, and any crystalline portion of it will be negligible. I am not sure whether it will crack or not. From my own experience of melting rocks, when you have a similar amount cooling down in Earth's atmosphere, they crack. But then, silicate glass does not crack when cooled down in air. I guess it comes down to the composition of the rock/glass.

The lava will not percolate down to the regolith. Lavas hardly penetrate soils on Earth, so it is probably not going to happen on the Moon where the gravity is much weaker.

If I were looking for construction materials on the Moon, I would just build a quarry. Seems easier than melting down dust.

> **Comments:**
> **username_0**: The regolith on the Moon is between 10 and 30 m deep, and on the very edge of a crater such as proposed, it is deeper as the surface has been folded back on itself by the impact blast. A quarry at the very beginning seems difficult, but there are plenty of large boulders. I don't know how hard it would be to cut them into precise shapes, i'll have to look into it.  
> **username_1**: @username_0 As hard as cutting basalt glass sheets into shapes? I guess that's one of the reasons we don't have colonies on the moon yet.  
> **username_0**: I had thought the cutting could be done just before the sheet froze. And the sheet can be melted into specific shapes in the first place.  

---

