Is it true that under certain conditions, Mg can reduce SiO2?

Is it true that under certain conditions, Mg can reduce $\ce{SiO2}$ and the latter the former? What are those conditions?




Yes it is true. 


Conditions are temperature in the 650 to 850 degrees C range. 


There is a [cool looking youtube video of the reaction](http://www.google.com/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=6&cad=rja&uact=8&ved=0CEcQtwIwBQ&url=http%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DMJ3oCT_HMoE&ei=7Qq5VPqNJo3ksATKxYLYCg&usg=AFQjCNEY1LEmWs661zxDe8Mmz9uD4EyADA), not that that makes it true.


For a more serious discussion see [Production and Purification of Silicon by Magnesiothermic Reduction of Silica Fume](https://tspace.library.utoronto.ca/bitstream/1807/25788/3/Sadique_Sarder_E_201011_MASc_thesis.pdf)


and [Ordered Mesoporous Silicon through Magnesium Reduction of Polymer Templated Silica Thin Films](http://pubs.acs.org/doi/abs/10.1021/nl801759x)


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Yes, it is true below $\pu{1683 K}$, the melting point of silicon, the $\Delta\_\mathrm{f}G^\circ$ curve for the formation of $\ce{SiO2}$ lies above the $\Delta\_\mathrm{f}G^\circ$ curve for $\ce{MgO}$, so, at temperature below $\pu{1683 K}$, $\ce{Mg}$ can reduce $\ce{SiO2}$ to $\ce{Si}$.


On other hand, above $\pu{1683 K}$ the $\Delta\_\mathrm{r}G^\circ$ curve for $\ce{MgO}$ lies above for $\ce{SiO2}$, hence at temperatures above $\pu{1683 K}$, $\ce{Si}$ can reduce $\ce{MgO}$ to $\ce{Mg}.$


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