glass slowly converts to quartz ?

[Widdekind]

I understand, that a "glass" is an amorphous semi-solid, whose molecular monomers have not self-assembled, into an ordered crystalline structure. A "glass" is a kinetically locked, rapidly cooled state, wherein the material was "flash frozen" before it could self-assemble, into an ordered, structured, crystalline, solid state. I.e. in contrast to the amorphous liquid state, wherein the molecular monomers "stick & slip"; in an amorphous semi-solid glass, the molecular monomers "stick & grip" or "stick & lock".

 

For example, glass is (essentially) amorphous semi-solid silicon dioxide (SiO₂) (chemically identical to carbon dioxide (CO₂), but much more massive, which is why the former is a solid ("sand"), whilst the latter is a gas, at terrestrial S.T.P.). And, the crystalline structured solid form of SiO₂, i.e. quartz crystal, is an ultimately-lower energy state, than the amorphous semi-solid form, i.e. glass.

 

Therefore, given sufficient time, e.g. geologic 'deep time', would not glass slowly solidify, into quartz crystal ? Would not small regions become aligned, and 'nucleate' the crystallization process, reminiscent of 'zone growth' in ferromagnets, albeit ultra-slowly ? And so, if quartz crystal is a common constituent, of continental crust, on earth today; then would not those crystals have derived, from amorphous glasses, billions of years ago, on the early earth ?

 

Also, if quartz is the most common constituent, of planetary crusts, then could not fiber-glass be generatable, in situ, from "ground up regolith", on any rocky world, e.g. moon, mars ? Could "concrete & fiber-glass" help build habitats, on other worlds, or remote regions of earth ?

 

 

 

Were anyone willing to delve into the details, I suspect, that there is some connection, between glass formation, and latent heat of fusion. I.e. a glass is a "flash-frozen" super-cooled melt, in a non-crystalline amorphous state, below its melt/freeze transition temperature T_m; and, even below its colder glass transition temperature T_g < T_m; but, above its theoretical Kauzmann temperature T_k < T_g < T_m, at which the "entropy", i.e. internal energy, of the super-cooled, flash-frozen "glass" would reduce to the value, of the true solid state. I suspect, that all of that entropy, i.e. internal energy, difference, corresponds to the latent-heat-of-fusion, released during solidification / crystallization, under "normal" conditions. If so, then the glass state would truly be transitory, although the transition, from amorphous liquid, to crystalline solid, could take ages & aeons, for some materials. For example, when water freezes to form ice, it would, then, briefly transition through a "glassy" state.

 

I understand, that, unlike in an amorphous liquid state, in an amorphous semi-solid glass state, covalent bonds do form, albeit "haphazardly". The stronger the bonding affinities, of the molecular monomers, in the initial liquid-phase "melt", the higher the glass transition temperature T_g ----> T_m. Conversely, non-interacting monomers would never "vitrify", i.e. become glassy, T_g ----> T_k. Naively, I intuit, that a "glass" is a possible condition, of a super-cooled liquid, which "should be solid", but hasn't given up (all) of its internal energy, i.e. latent heat of fusion, and so retains a liquid-like amorphous unstructuredness.

 

On other, colder, worlds, could dry ice, i.e. solid CO₂, exist in glassy, as well as crystalline, (semi-)solid forms ?

Edited March 4, 2012 by Widdekind

[John Cuthber]

Glass does slowly crystallise and fused quartz will (even more slowly) revert to quartz.

http://en.wikipedia.org/wiki/Devitrification

 

Carbon dioxide (which is not, of course, chemically identical to SiO2) won't readily make the same sorts of structures.

On the other hand, aluminium phosphate forms different structures that mimic SiO2

[Widdekind]

if fiber-glass is similar, in strength, to many metals; then could rail-road tracks be "extruded", from fiber-glass? In analogy to "extruded" PVC piping, such rails could be continuously created, from traveling trucks, into which the appropriate ingredients could be continuously poured, so that continuous rails could be extruded, vaguely like line-painting-trucks on roads, capable of creating continuous road markings.

[Iggy]

Here is a good link on train wheel and track materials and forces: Modern Tribology Handbook, Volume 1, 34.2

 

The compressive strength of strong fiberglass, according to wiki, is 350 MPa and from the link train wheels exert pressure in the hundreds of Mpa. It also says the contact point has a temperature of "several hundred degrees Celsius in normal operation"... so I think it would fail or deform before it had a chance to wear out.

[Ophiolite]

Also, if quartz is the most common constituent, of planetary crusts, then ...

Just as clarification: quartz is not the most common constituent of planetary crusts. It is probably common (but not the most common) only on the Earth. Silica is the most common consitutent, but it is tied up in silicate minerals, primarily olivines, feldspars and pyroxenes. Only in the acidic rocks making up continental crust is quartz commonplace.

[John Cuthber]

Incidentally, (at the risk of getting this wrong and being eaten by the geologists here) I'm pretty sure that those lovely quartz crystals you see in rock shops were formed from solution, rather than a melt.

Quartz can't crystallise from a melt because there's a high temperature solid form (or two) that forms first.

http://en.wikipedia.org/wiki/Tridymite

 

http://en.wikipedia.org/wiki/Cristobalite