Quartz is Not Glass. So What?

This is part of a series of articles responding to the claims made in Dean Sessions’ Universal Model.  Click the link to see the introduction to the series.

Quartz is not glass!  According to Dean Sessions, this is one of the most critical points of the Universal Model (UM), and it completely undermines standard geological theories (see vol. 1, ch. 5 of the UM).  Apparently, he took a blowtorch to some quartz crystals in his garage, melted them, and when they cooled, they were glass, not quartz!  Quartz can’t grow from a melt, he says, so when we see quartz in igneous rocks like granite, it can’t possibly have grown from magma.  (Remember that he doesn’t think magma exists.)  It turns out that the “evidence” presented by Sessions does NOT really challenge current geological theory.  He misread some of his information and ignored a whole lot of information that directly contradicts his claims.  To show you how he went wrong, first I’m going to have to back up and explain a few things.  

What is Quartz?

Quartz is a mineral with the chemical formula SiO2, and like almost all minerals, it is a crystalline solid.  Crystalline solids have a certain pattern of atoms that is repeated over and over in three dimensions.  Due to this repeating pattern, a single crystal can take on certain characteristic forms, bounded by flat crystal faces that exhibit the same symmetry as the internal, molecular-scale structure.

What is Glass?

Glass is a kind of non-crystalline solid.  It’s solid, so its atoms don’t move around as much as in a liquid or gas, but the arrangement of the atoms is more irregular than in a crystal.

How are Crystals and Glasses Different?

Since the properties of a solid depend both on its chemical composition and its molecular-scale structure, the properties of a glass and a crystal with the same chemical composition (such as SiO2 as quartz and SiO2 glass) can have quite different properties.

Glasses are formed rather than crystals when the solidification process happens too quickly for a precise crystal structure to be built.  The atoms are frozen in place in a structure that is very much like the liquid it came from.  With a somewhat slower solidification process, small crystals can form, often making polycrystalline aggregates.  With an even slower process, large crystals can form.

Another difference between crystalline solids and glasses is that the chemical compositions of crystals are much less variable.  Since crystals have a 3-D repeating pattern of atoms, substituting in impurities for the main elements can only happen where there is room in the structure for the impurity.  Otherwise, the structure will be disrupted too much to continue growing in three dimensions.  Glasses, like liquids, can have continuously variable compositions over a wide range.  One consequence of this is that a liquid might solidify to form more than one type of crystal, with different structures that will accommodate the various elements present, but a glass formed from the same liquid would have a single composition throughout.

How Can You Tell if Something is Crystalline?

To tell if a solid is crystalline, you can look at the outward form to see if it has a characteristic crystal shape, but crystals don’t always have such regular shapes.  Often, crystals will simply fill in the space available for them, and can grow irregularly for a number of other reasons.  And if you take a hammer to a crystal and break it into tiny pieces, those tiny pieces will still have the same properties and molecular-scale structure as a nicely shaped, large crystal.  The repeating molecular-scale structure, not the outward shape or anything else, is what defines a solid as crystalline.

The most foolproof method for detecting a crystalline structure is X-Ray Diffraction.  If you shoot X-rays all with the same wavelength at a crystal, the atoms will absorb the rays, and them scatter them back out in all directions.  Due to the periodic molecular-scale structure, there will be certain angles at which the scattered X-rays reinforce each other, and other angles where they cancel each other out.  Below I show powder X-ray diffractograms for quartz (green), the same quartz with much smaller particles (red), and SiO2 glass (black).  You can see the nice, sharp peaks at certain angles for the larger quartz particles, whereas the peaks get shorter and broader when the particles are much smaller.  The pattern for a glass just looks like one broad hump.

Are There Other Forms of SiO2?

It is possible to have multiple crystalline substances that have the same chemical formulas, but different molecular-scale structures.  These are called polymorphs.  Higher pressure tends to favor more densely packed structures, while higher temperature tends to favor more less densely packed, and more symmetrical structures, so different polymorphs will be stable under different conditions.  Below is a phase diagram showing the pressure and temperature ranges where the different silica (this refers to the formula SiO2) polymorphs are stable.  At or near Earth surface conditions, alpha-quartz is the most stable.

Can One Polymorph of SiO2 Turn Into Another?

The short answer is YES, although Dean Sessions (pp. 101-102) apparently thinks otherwise.  Here’s the long answer.

There are two types of transitions between polymorphs:  displacive and reconstructive.  In a displacive transformation, none of the original chemical bonds are broken, and no new bonds are formed.  Instead, the atoms shift positions relative to one another in a concerted motion.  Since no bonds are formed or broken, there is essentially no energy barrier to overcome for such a reaction to proceed, and so it always happens.  For example, the transition between alpha- and beta-quartz is displacive, so once you raise the temperature above the transition shown in the phase diagram, the transformation will take place, no matter what.  The same is true when you cool down beta-quartz.  The animated gif below shows how the quartz structure changes as it goes through the alpha-beta transition.  (This is a “polyhedral” representation of the structure, where there are oxygen atoms at the corners of the tetrahedra and silicon atoms in the middle of the tetrahedra.)

It turns out that there are also alpha- and beta- varieties of both tridymite and cristobalite, with displacive transformations between them.  However, there wasn’t room to depict that on the phase diagram above.

During a reconstructive transformation, bonds are broken and new ones are formed, so there is an energy barrier to the reaction.  The consequence is that if the system crosses the stability boundary too fast, the transformation might not happen.  This way, the less stable form can persist for a very long time in a “metastable” state.

Therefore, even though alpha-quartz is the stable phase under Earth-surface conditions, metastable phases like stishovite, coesite, tridymite, and cristobalite can persist under those conditions if they crossed stability boundaries too fast.  However, beta-quartz never occurs under Earth-surface conditions, because its transition to alpha-quartz can’t be stopped.

Have Transformations Between SiO2 Polymorphs Been Observed?

Sessions would have us believe, however, that none of the transitions shown on the silica phase diagram ever happen.

We know the physical properties of coesite and other high pressure. high temperature, silica-based minerals depicted in the Silica Phase Diagram, because of laboratory experiments conducted by scientists who were able to produce these minerals.  After mineral formation, temperature and pressure return to normalized conditions and researchers observe and measure the physical properties of the minerals, such as density and crystal structure. Once heated, the minerals do not revert to natural quartz after they cool and/or with pressure reduction; the properties and crystalline structure of the minerals are preserved, remaining as they were when formed..  (pp. 102-103)

This is demonstrably false, and provides a perfect example of how Dean Sessions appears to be such a zealot for his pet theories that he is emotionally incapable of recognizing contradictory data.  Here are just a few examples of this contradictory data.

In 2013, some Italian scientists who study ceramics published a paper called “A kinetic study of the quartz–cristobalite phase transition” in the Journal of the European Ceramic Society.  (Chemical “kinetics” is the study of reaction rates.)  They took ground alpha-quartz, put it in a powder X-ray diffractometer that can operate at high temperatures, and then took a look at how the diffraction patterns changed with temperature and particle size of the beginning quartz. Below is one of their figures, showing how the diffraction patterns for the largest (A) and smallest (B) starting quartz particles change with temperature in the angle range where the main quartz and cristobalite peaks reside.  At the lowest temperatures, there is a clear shift in the positions of the peaks, coincident with the (unstoppable!) transition from alpha- to beta-quartz.  At higher temperatures, the quartz peaks start to shrink, and a new peak appears, indicating the presence of cristobalite.

In 1997, geologists at Stanford and the U.S. Geological Survey published a study called “Kinetics of the coesite to quartz transformation” in Earth and Planetary Science Letters, in which they reported… transforming coesite to quartz at elevated temperature and pressure.

As if that weren’t enough, a couple glass scientists from the Alcoa corporation wrote in a 1994 paper in the the Journal of Materials Research that they were able to make cristobalite by sintering (not melting!) high-silica glass in the presence of borosilicate glass.  Some Japanese ceramic scientists transformed both quartz and amorphous silica (much like silica glass) into coesite at high pressures and temperatures.

I could go on, and On, and ON.

Can Quartz and Other Minerals Grow From Melted Rock?

It is well known that quartz (and many other minerals) can grow from a hydrothermal solutions (hot, pressurized water with silica dissolved in it), both in nature and the lab.  Sessions has grown large quartz crystals this way himself, and that’s the way synthetic quartz crystals are grown for technological applications.  He asserts that this is the only way quartz and most other minerals can be grown, however, and that no minerals ever grow from melted rock.  Is that true?

Sessions provides two main lines of “evidence” for his claims.  First, if you take a blowtorch to a rock and melt it, then let it cool, you get glass, rather than crystals (pp. 103-104).  Second, people who grow quartz in the lab for industrial purposes say that you can’t do it by starting with a melt.

Considering how lazy Dean Sessions was about looking for experiments involving transformations between SiO2 solid phases, I am profoundly unsurprised to report that he did the same thing with regard to growth of quartz from a melt.

Consider that quartz can, in fact, be grown from a melt.  Oh, and Dean Sessions knows it.

For instance, back in 1975 geologists from Denmark and the U. of Chicago published a paper called “Water content of a granite magma deduced from the sequence of crystallization determined experimentally with water-undersaturated conditions” in Contributions to Mineralogy and Petrology.  They reported experiments in which they ground up some granite, melted it into a glass, ground up the glass, put it in a heated, pressurized reaction vessel with variable water content, and baked it for up to a month.  (They couldn’t run longer experiments because their reaction vessels wouldn’t hold up.)  The melted and recrystallized material was then examined using X-ray diffraction and optical microscopy methods.  Yes, they made quartz.  And they made the other minerals that are in granite, too.  Lots of other experimental petrologists have done the same thing.

So why does Dean Sessions say the following?

Ask any geologist if they know of anyone who has made granite and they cannot say. Science can reproduce the temperature and pressure required to make granite according to the modern magma theory, yet scientists cannot synthesize it. (p. 123)

In chapter 6, he quotes a geologist saying the following.

Plutonic textures have not been duplicated in the laboratory, however. The complete crystallization of the interstitial liquid as large crystals has not been achieved in granitic melts.  (p. 161)

Oooohhhhh… now I get it.  Sessions is objecting that these synthetic granites have smaller crystals than you find in natural granites… that are thought to have crystallized over tens of thousands of years.  (When geologists talk about “plutonic textures,” they are mainly talking about the size of crystals in an igneous rock that formed underground.)  He might also be talking about how sometimes crystals don’t exhibit characteristic crystal faces when the growth process is diffusion-controlled.

The tortured nature of the “logic” exhibited in the UM is astonishing.  Sessions knows perfectly well that various minerals, including quartz, can be synthesized from a melt, because he writes about the experiments of Norman Bowen.  He quotes Wikipedia:

He experimented in the early 1900s with powdered rock material that was heated until it melted and then allowed to cool to a target temperature whereupon he observed the types of minerals that formed in the rocks produced. He repeated this process with progressively cooler temperatures and the results he obtained led him to formulate his reaction series which is still accepted today as the idealized progression of minerals produced by cooling magma.  (p. 123)

Sessions goes on to point out that Bowen’s theories developed in the early 1900s were later largely altered, but that cannot change the fact that Bowen synthesized various igneous minerals INCLUDING QUARTZ from molten material.  Note, for instance, that Bowen even reported synthesizing both quartz and tridymite from pure silica glass by melting and crystallizing it in the presence of water vapor.  (See O.F. Tuttle and N.L. Bowen, Origin of Granite in the light of experimental studies in the system NaAlSi3O8-KAlSi3O8-SiO2-H2O, Geological Society of America Memoir 74, 1958, p. 29)

Ok, so experimental petrologists haven’t been able to produce synthetic granite that is exactly like natural granite in every single way.  But they have synthesized granite that has the same minerals as natural granites.  If that isn’t satisfying for Dean Sessions, then there is a simple solution.  He can synthesize granite with something closer to the right texture using hydrothermal methods.  I’m willing to bet he can’t do it, but for now I’m hoping that he will stop sowing confusion about what scientists have managed to do.

Why Don’t Quartz Crystal Manufacturers Use Melt Growth?

As I mentioned above, one of Sessions’ lines of “evidence” is that people who grow quartz in the lab for industrial purposes say you can’t do it by starting with a melt.

Here’s how Dean Sessions introduces the topic.

During our magma research, it became quickly apparent that there were two camps when it came to investigating and explaining mineral growth. The first camp–the theoretical group–consisted of “magma theorists,” the geologists. The other camp, the “capitalists” included the mineralogists and engineers driving the discovery of new marketable technology worthy of exploitation. The two camps not only had different goals, they worked on very different experiments in markedly different social environments under completely different paradigms, for completely different reasons.

The magma theorists/geologists labored at the universities, while the mineralogists and technologists occupied technology and research centers such as the well–known Bell Laboratory both published technical papers, the magma theorists’ latest theories attempted to explain how natural minerals should form from cooling magma while the technologists actually produced the minerals and got better at it. The lab – grown minerals they made were nearly identical to natural minerals and they kept getting better.

One primary difference between the two camps is how they receive their funding. Theorists develop new theories, and solicited grant money through government directed organizations to obtain funding. The technologists, on the other hand, worked in privately funded labs seeking ways to produce higher-quality minerals faster and at lower prices. It is not difficult to guess which group provided the best information about how minerals actually form.  (p. 104)

So given that quartz demonstrably CAN be synthesized from a melt, does this mean all those crystal engineers Sessions quotes are ignoramuses?  No, they aren’t, but I’ll try to show you what’s going on.

Sessions quotes a group of gemstone synthesis experts as follows.

“Quartz cannot be grown from a melt… because silicon dioxide (quartz) melts are so viscous that tbey form glasses rather tban crystals when they are cooled.  (p. 105)

Here’s the thing.  Silicate melts (like the ones that form granite) become more and more viscous (thick and sticky) as their silica concentration increases.  Because the liquid is so viscous, it takes longer for atoms and molecules in the melt to move around, and so crystal growth is slower and more difficult.  If you take a crystal of quartz, which is pure silica, and melt it, you will have a melt that is even more viscous than the kind that forms  granite, and crystallization will be even more difficult and slow.  Crystallizing from a melt in the presence of water vapor under pressure, like Bowen did, can speed things up, at least somewhat.

Now, if you were someone manufacturing synthetic quartz crystals, would you want to wait around who knows how long to see if you could get some small crystals to form from a melt, or would you want to use a hydrothermal method to quickly grow nice, big, perfect crystals?  Can you also see why it would be easier to synthesize quartz in less viscous, granitic melts than pure silica, but then other, unwanted, minerals would form there as well?

Does Quartz Piezoelectricity Prove It’s Not Magmatic?

Sessions isn’t done, however.  He thinks that the piezoelectric properties of quartz are the real clincher.

The piezo (pee-ay-zo) electrical property of quartz-based (silicates) rocks is one of the most important components in the Earth’s energy field. This property, the piezoelectric effect, diminishes almost entirely by heating quartz rocks above 570 °C.  This is direct evidence that the quartz-based rocks, ubiquitously abundant on the continents, could not have formed from melted rock because that requires temperatures exceeding 1200 °C. (p. 105)

Piezoelectric materials build up electrical charge when subjected to mechanical stress, and there are many technological applications for such materials.  Sessions quotes one of his “technologists” to explain what this has to do with the melt question.

At a temperature of approximately 573° C, quartz transforms from Alpha to Beta quartz. During the transformation, most of the piezoelectric characteristics are lost, rendering Beta quartz unsuitable for the manufacture of crystal units. (p. 106)

The author of the online newsletter article from which Sessions mined that quote, Louis Bradshaw, has indeed worked as crystal engineer, but he does not even have a bachelor’s degree, so perhaps we can excuse him for muffing one or two technical details.

First, of course beta-quartz will form from a melt (see the phase diagram above), but as it goes down in temperature, it will inevitably change to alpha-quartz; it can’t be prevented.  So what is the problem?  It is explained pretty well (but in marginal English) in this brochure by a Swiss manufacturer, QuartzCom.

Natural quartz was used as raw material up to the 1960s for the production of quartz crystals. But Giorgio Spezia discovered already in 1900 at the University of Turin in Italy the hydrothermal growing of quartz. His autoclave was small and gas heated. He produced the first usable synthetic quartz stones. The growing of quartz can not be done from the melted material. Quartz has an inversion point at 573°C where the structure changes from low temperature alpha quartz (piezoelectric) to the high temperature beta quartz (no more piezoelectric). On the way from high to low temperatures, the crystal goes back to the alpha quartz structure. But from the alpha quartz exist two crystallographic versions, the right handed and the left handed crystal. This produced twins, means parts of the crystal are left handed and another part is right handed. This gives a totally different behavior of the final product. Such crystals are no more of use to the crystal industry.

Take another look at the above animation of the alpha-beta quartz transition. It’s essentially a matter of the SiO4 tetrahedra twisting, but when beta-quartz makes the transition, it can either twist to the right or the left.  This makes a certain chain of tetrahedra in the structure either make a right- or left-handed spiral, so a single crystal of beta-quartz might transition into an alpha-quartz crystal that has right- and left-handed domains.  These crystals are called Dauphiné twins, if you are interested.  This German website about quartz explains how this affects the piezoelectric properties of the crystal.

Dauphiné Law twins are electrical twins: their optical properties are similar to untwinned crystals, but mechanical pressure along the a axis does not cause an electrostatic polarization of the crystals.

In other words, the right-handed and left-handed zones of such an alpha-quartz crystal have piezoelectric properties are polarized in opposite directions, and so cancel each other out. That is why nobody uses natural quartz crystals for electronics, anymore.

Do Quartz and Other Minerals Form from Melts in Nature?

Sessions seems to believe that molten rock does exist (just not very deep in the Earth), and that it sometimes spews out of volcanoes and solidifies to create new rock.  But what does he think these rocks are made of?   I’m not completely sure–even after reading all about “The Rock Cycle Pseudotheory” in chapter 6.  I’m guessing, however, that Sessions doesn’t think anything but glass can be produced by solidifying lava, because he actually makes the argument (p. 105) that the Earth and the other planets could not have been formed from molten material because, “There are no known glass planets!”

The fact is, however, that volcanic rocks–even the ones collected fresh out of the volcano vent–are not all glassy.  Glassy textures occur at the tops of lava flows or in material ejected high into the air from the vent.  But other than that, the rest is made of… CRYSTALS.  Yes, crystals, not glass.  They may be small, but you can still detect them with X-ray diffraction.  A team of British geologists, for instance, recently published a study titled “Controls on variations in cristobalite abundance in ash generated by the Soufriére Hills Volcano, Montserrat in the period 1997 to 2010 “.  These guys went in and collected the ash, often on the same day it erupted.  Then they analyzed it using various methods including X-ray diffraction.  In addition to the glassy material that is always in volcanic ash, they also found significant amounts of BOTH cristobalite and quartz!  A team of Argentinian and Italian geologists did something similar in their paper, “Pyroclasts of the First Phases of the Explosive-Effusive PCCVC Volcanic Eruption:  Physicochemical Analysis” in Advances in Materials Physics and Chemistry.  Here are a couple of their X-ray diffraction patterns.  The one on the left is for some ash that has just glassy material, and the one on the right has both glassy and crystalline material, including quartz, plagioclase feldspar, and magnetite.

FACT:  Crystalline minerals form from molten rock in nature.  

Book Learnin’

“The fact that ‘quartz cannot be grown from a melt,'” says Sessions, “is one of the most important geological facts that modern geology seems to have completely overlooked” (p. 105).  Or at least it would be, if it weren’t false.

Dean Sessions’ arguments about quartz and mineral formation from melts are demonstrably, utterly wrong.  Laughably wrong.  And a lot of that is because he is ignorant of the relevant technical details, and hasn’t bothered to read the kind of books that would educate him.   Rather than brushing off Earth scientists for being “[s]teeped in the magma tradition because of their book learning” (p. 105), maybe he should try harder to understand their points of view and engage with their arguments.

I have no reason to believe he is insincere, or even unintelligent.  But I have seen every reason to believe that he is only capable of dealing with information that seems consistent with his preconceived notions.  Even if he reads something contradictory, he doesn’t seem capable of processing it, so “book learning” can only do so much for him.  Consider this example.  I mentioned above that Sessions quoted one geologist as follows.

Plutonic textures have not been duplicated in the laboratory, however. The complete crystallization of the interstitial liquid as large crystals has not been achieved in granitic melts.  (p. 161)

The source of this quotation is Paul Hess (1989) Origins of Igneous Rocks, p. 70.  I imagine we can assume that Dean Sessions read the whole paragraph, can’t we?  Because here are some other passages from the very same paragraph.

Coarse-grained plutonic rocks are produced over several millions of years of slow cooling and crystallization.  Nevertheless, experiments show that feldspars of the size and shape typical of plutonic rocks can be grown in a matter of days or weeks in the laboratory….  Peak growth rates of feldspar and quartz in hydrous granitic melts are in the range of 10^-6 to 10^-8 cm/sec, and growth rates of plagioclase, pyroxene, and olivine are even greater in more depolymerized melts.  Even the slowest growth rates are capable of producing crystals several centimeters in diameter in a few years.  The very slow cooling rates of deep-seated rocks are not necessary for the formation of large crystals.  (Emphasis added.)

So either Sessions didn’t even read the entire paragraph he quote-mined, which is bad enough, or he is lying when he repeatedly says quartz and other minerals can’t crystallize from a melt.  Oh, I don’t necessarily mean that he deliberately tells falsehoods, but lying to yourself is still lying, after all.

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