Quartz Stars

Stars start off doing hydrogen burning, making helium. Then they transition to helium burning. From that point onwards, most of the pathway is added helium, so things step up by helium units. There are a fair number of loose neutrons and protons so some side reactions step up by one mass unit, making the miscellaneous atoms of the universe. Eventually this ends at the area of iron and nickel as there is no more nuclear “binding energy” to release. Then the star, if big enough, explodes in a nova event, creating the heavier elements as byproducts of that energetic final collapse. That rare process is also why elements like gold and uranium are rare.

That’s the typical thumbnail sketch of stellar life cycle. But I think it skips over a couple of very important points. I’ll mostly quote from the Wiki for these, as this topic isn’t prone to political screwage.

Have you ever wondered why we have so many rocks dominated by Silicon and Oxygen? Not just quartz, but things like feldspar?



Feldspars (KAlSi3O8 – NaAlSi3O8 – CaAl2Si2O8) are a group of rock-forming tectosilicate minerals that make up about 41% of the Earth’s continental crust by weight.

Feldspars crystallize from magma as veins in both intrusive and extrusive igneous rocks and are also present in many types of metamorphic rock. Rock formed almost entirely of calcic plagioclase feldspar is known as anorthosite. Feldspars are also found in many types of sedimentary rocks.

Note those elements. Why so much of them? The nickel iron core of the planet makes sense as lots of that is made in end of life stars. But oxygen? Silicon? Magnesium? Calcium? Aluminum?

Blame the stars.

Alpha Importance (not just for dogs)

Stars like to fuse atoms in units of 4 mass number, via alpha particles. A helium 4, ignoring or removing the electrons. So as soon as hydrogen burning starts piling up the helium, alpha particles become the next big thing. But Carbon is more stable than Beryllium so you get a lot of carbon:


Triple-alpha process in stars

Helium accumulates in the cores of stars as a result of the proton–proton chain reaction and the carbon–nitrogen–oxygen cycle. Further nuclear fusion reactions of helium with hydrogen or another alpha particle produce lithium-5 and beryllium-8 respectively. Both products are highly unstable and decay almost instantly back into smaller nuclei, unless a third alpha particle fuses with a beryllium-8 nucleus before that time to produce a stable carbon-12 nucleus. The half-life of 5Li is 3.7×10^−22 s and that of 8Be is 8.19×10^−17 s. When a star runs out of hydrogen to fuse in its core, it begins to contract and heat up. If the central temperature rises to 10^8 K, six times hotter than the Sun’s core, alpha particles can fuse fast enough to produce significant amounts of carbon:

The net energy release of the process is 7.275 MeV.

As a side effect of the process, some carbon nuclei fuse with additional helium to produce a stable isotope of oxygen and energy:
Fusing with additional helium nuclei can create heavier elements in a chain of stellar nucleosynthesis known as the alpha process, but these reactions are only significant at higher temperatures and pressures than in cores undergoing the triple-alpha process. This creates a situation in which stellar nucleosynthesis produces large amounts of carbon and oxygen but only a small fraction of those elements are converted into neon and heavier elements. Oxygen and carbon make up the main “ash” of helium-4 burning.

Note that before the oxygen accumulates, we have a carbon star, with helium.

Then oxygen accumulates. Carbon, and oxygen…

So what we have here is basically a CO or CO2 star. Ever wonder why planetary atmosphere has a lot of CO2? Now you know.

Helium, mass 4, beryllium mass 8 unstable, carbon mass 12, oxygen mass 16, etc.

You would expect neon at 20, Magnesium at 24, silicon at 28.

Carbon Nuclear Burning


Reaction products

This sequence of reactions can be understood by thinking of the two interacting carbon nuclei as coming together to form an excited state of the 24Mg nucleus, which then decays in one of the five ways listed above. The first two reactions are strongly exothermic, as indicated by the large positive energies released, and are the most frequent results of the interaction. The third reaction is strongly endothermic, as indicated by the large negative energy indicating that energy is absorbed rather than emitted. This makes it much less likely, yet still possible in the high-energy environment of carbon burning. But the production of a few neutrons by this reaction is important, since these neutrons can combine with heavy nuclei, present in tiny amounts in most stars, to form even heavier isotopes in the s-process.

The fourth reaction might be expected to be the most common from its large energy release, but in fact it is extremely improbable because it proceeds via electromagnetic interaction, as it produces a gamma ray photon, rather than utilising the strong force between nucleons as do the first two reactions. Nucleons look a lot bigger to each other than they do to photons of this energy. However, the 24Mg produced in this reaction is the only magnesium left in the core when the carbon-burning process ends, as 23Mg is radioactive.

The last reaction is also very unlikely since it involves three reaction products, as well as being endothermic — think of the reaction proceeding in reverse, it would require the three products all to converge at the same time, which is less likely than two-body interactions.

The protons produced by the second reaction can take part in the proton-proton chain reaction, or the CNO cycle, but they can also be captured by 23Na to form 20Ne plus a 4He nucleus. In fact, a significant fraction of the 23Na produced by the second reaction gets used up this way. In stars between 9 and 11 solar masses, the oxygen (O-16) already produced by helium fusion in the previous stage of stellar evolution manages to survive the carbon-burning process pretty well, despite some of it being used up by capturing He-4 nuclei. So the end result of carbon burning is a mixture mainly of oxygen, neon, sodium and magnesium.

The fact that the mass-energy sum of the two carbon nuclei is similar to that of an excited state of the magnesium nucleus is known as ‘resonance’. Without this resonance, carbon burning would only occur at temperatures one hundred times higher. The experimental and theoretical investigation of such resonances is still a subject of research. A similar resonance increases the probability of the triple-alpha process, which is responsible for the original production of carbon.

Notice how that mix of elements is starting to look a lot like the stuff in various rocks…

I’d also note in passing that perhaps investigating similar “resonance” effects could help explain LENR effects.

But we are still short of silicon.

We need further reactions in stars to create it.

Oxygen Nuclear Burning

I’m skipping a step here, but it is basicslly just consuming the neon made. Neon gets turned into oxygen and magnesium.


Why neon, heavier than oxygen, burns first is covered in the oxygen burning wiki

Pre-oxygen burning

Although 16O is lighter than neon, neon burning occurs before oxygen burning, because 16O is a doubly-magic nucleus and hence extremely stable. Compared to oxygen, neon is much less stable. As a result, neon burning occurs at lower temperatures than 16O + 16O. During neon burning, oxygen and magnesium accumulate in the core of the star. At the onset of oxygen burning, oxygen in the stellar core is plentiful due to the helium-burning process (4He(2α,γ)12C(α,γ)16O), carbon-burning process (12C(12C,α)20Ne, 12C(α,γ)16O), and neon-burning process (20Ne(γ,α)16O). The reaction 12C(α,γ)16O has a significant effect on the reaction rates during oxygen burning, as it produces large quantities of 16O.

Thus making neon not so common in the world.


Oxygen-burning process

The oxygen-burning process is a set of nuclear fusion reactions that take place in massive stars that have used up the lighter elements in their cores. Oxygen-burning is preceded by the neon-burning process and succeeded by the silicon-burning process. As the neon-burning process ends, the core of the star contracts and heats until it reaches the ignition temperature for oxygen burning. Oxygen burning reactions are similar to those of carbon burning; however, they must occur at higher temperatures and densities due to the larger Coulomb barrier of oxygen.
Overall, the major products of the oxygen-burning process are 28Si, 32,33,34S, 35,37Cl, 36,38Ar, 39,41K, and 40,42Ca. Of these, 28Si and 32S constitute 90% of the final composition.The oxygen fuel within the core of the star is exhausted after 0.01–5 years, depending on the star’s mass and other parameters. The silicon-burning process, which follows, creates iron, but this iron cannot react further to create energy to support the star.

During the oxygen-burning process, proceeding outward, there is an oxygen-burning shell, followed by a neon shell, a carbon shell, a helium shell, and a hydrogen shell. The oxygen-burning process is the last nuclear reaction in the star’s core which does not proceed via the alpha process.

Note again that we are collecting elements common in rocks, like Calcium and Potassium, along with the silicon.

At about the 1/3 point of the oxygen burn cycle, we basically have a star made of SiO2. In effect, a quartz star. Talk about crystal power!


Or, given the other elements kicking about, I suppose you could call it a feldspar star…

So how does this stuff get to make planets? Why doesn’t it all just end up iron?

Well, sometimes things blow up.

Pair-instability supernovae

Very massive (140–260 solar masses) population III stars may become unstable during core oxygen burning due to pair production. This results in a thermonuclear explosion, which completely disrupts the star.

We are literally made of, and live on, the ashes of stars. The end result of a quartz star explosion.

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About E.M.Smith

A technical managerial sort interested in things from Stonehenge to computer science. My present "hot buttons' are the mythology of Climate Change and ancient metrology; but things change...
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17 Responses to Quartz Stars

  1. Larry Ledwick says:

    Sound waves generated by iron core collapse, may be the final driver for super nova explosions, which then blow off the outer shells of dying stars which are rich in carbon, oxygen and other heavier elements and spread their contents through out the cosmos, creating the dust clouds were future starts are born.


  2. Larry Ledwick says:

    Interesting that this came out at this time – ref the Younger Dryas
    “We conclusively have identified a thin layer over three continents, particularly in North America and Western Europe, that contain a rich assemblage of nano-diamonds, the production of which can be explained only by cosmic impact,” Kennett said. “We have also found YDB glassy and metallic materials formed at temperatures in excess of 2200 degrees Celsius, which could not have resulted from wildfires, volcanism or meteoritic flux, but only from cosmic impact.”


  3. Larry Ledwick says:

    I would like to see this deposit map laid over a spherical globe rather than being distorted by flat map projections.

    The Australian deposits strike me as suspiciously similar to the shrapnel pattern of an exploding mortar or artillery shell.


    See crater analysis illustrations in this document page 1-6 for example.

    Click to access 1992_US_Army_CRATER_ANALYSIS_AND_SHELL_REPORTS_49p.pdf

  4. Larry Ledwick says:

    Preceding 3 comments should have been over on the “I Know It’s Not Friday”

  5. Scissor says:

    Don’t forget biology and chemistry with regard to atmospheric composition. Our air is 78% nitrogen (N2).

  6. E.M.Smith says:

    OK. Our air is mostly nitrogen because biology and chemistry sequestered most of the CO2 in carbonate rocks.

  7. cdquarles says:

    I will add that this sequence of nuclear chemistry was known back in the 70s, at least, since I was made aware of it in the mid 70s.

  8. E.M.Smith says:

    That’s when I learned it. “Geology of the Solar System” I think it was called. U.C. Geology class. When I was on my geology kick :-) Studying the “geology” of stars and other planets seemed like a strange idea, so I signed up!

    What hit me new this time was realizing that the star is not just a hydrogen ball where some of these reactions happen, but fundamentally a different chemistry. A star made up of quartz, or a “CO2 Gas Giant” undergoing fusion… a CO2 Star.

    Odd to think that many of the stars you see glowing so brightly are quartz, or CO2, or Feldspar… just fusing away….

    Somehow I’d just learned the reaction sequence without thinking about the whole star becoming the new stuff. Though in really big stars you get layers of material and reactions. Even that’s a bit odd. A CO2 shell reacting away over a quartz core… or perhaps there is enough Mg to have a dolomite carbonate shell over a quartz core. A star that’s just a giant rock.

  9. Larry Ledwick says:

    I also learned the fusion sequences (although had not thought about it in ages) in about 7th grade ( circa 1965), where the progression moves up through the heavier elements till it gets to iron and then suddenly goes net negative in energy and the star implodes briefly reaching sufficient temperatures and pressures to create the higher elements before either blowing up in a nova or collapsing into a neutron star, or black hole, while blowing off a portion of itself into the cosmos.

  10. Gary says:

    So after the supernova when the debris coalesces into planets, how are the various elements combined into minerals? And more specifically, if gold is a rare element, what processes generate nuggets of mostly pure gold?

  11. Larry Ledwick says:

    When the planet forms at some point gravitational compression and heat from radioactive decay and small body impacts heats the material to melting temperatures. Once that happens various processes sort the chemicals into various minerals, depending on temperature pressure and time conditions different minerals crystallize out of the melt.

    Gold and quarts form as super heated water saturated solutions at high pressure cool.


    Its hard to imagine things like gold or quartz being dissolved by water solutions, but if the water is hot enough, the pressure high enough, and the chemistry is right (acids, and other elements like sulfur are present), then gold, quartz and other things you don’t expect to see dissolving will go into solution. The solutions move by natural convection (hot things rise), and as they rise the waters cool as they move farther from the heat source in the ground and closer to the surface. The gold is combined with sulfur to form gold-sulfur chemicals that dissolve in the water. I have specifically decided to avoid going into the geochemistry of gold solutions in this whole discussion, because I just don’t think it’s necessary to do that. The important fact is that at heat and temperature, gold will react with sulfur and other elements to form soluble chemicals. These chemical complexes are not all that stable, so that when the waters cool and the pressure drops, the chemicals decompose, releasing the gold to form nuggets. Sulfur is very common in geothermal waters (like hydrogen sulfide – the odor of rotten eggs). Most natural hot springs have that sulfur odor quite strong, and most gold – quartz veins have at least some sulfides like pyrite present.

  12. E.M.Smith says:

    You find good gold veins in volcanic areas where that hot sulphurous water is plentiful to do the natural leaching and concentrating. There is a volcanic “fountain” somewhere on the Nevada side of a volcanic field where the liquids are arriving at the surface and depositing metals (not much gold though) showing the processes still operating.

    The basic process is gravity sorting things by density, while chemistry causes density changes as different heat and pressure conditions change what compounds exist and which dissolves in what, or separates out.

    The particulars vary with the thousands of minerals that exist. Copper being most interesting as there are 3 or 4 useful ores AND occasionally native metal. All from different conditions in their making. Like gold, the metal is heavy, but various solutions can be light and percolate upwards, then react with other more reactive things, leaving metal behind. We do an artificial form of that in refining metals via a redox reaction. Mix carbon and ore, burn it, get CO2 , metal, and sometimes other stuff (like sulphur oxides if the ore is a sulphate instead of an oxide)

    That’s why California was a Gold Rush place. Volcanic sorting of gold into melted quartz rock veins underground, separated from the granite, then the mountains erode.

  13. cdquarles says:

    Don’t forget that supercritical water has a *much* different solution chemistry than low pressure and temperature water. The water molecule reorganizes. At the right conditions, chemical reactions happen *fast*. Hot stuff means that the internal kinetic energy is high; which means it is moving quickly, and doing so in all 3 physical dimensions. Ordinary gases at Earth surface conditions are moving at about 1 km/s, which is why sound travels at a diffusion limited biased random walk velocity in it and that’s about 300 m/s. For the same overall KE, the ‘lighter’ ones move faster; yet do not forget that the KE of a sample of matter is not a singe value. It is a range of values such that the thermodynamic temperature is a kind of a geometric mean. Also, the pressure is related to that internal kinetic energy, too, as in how hard atoms and molecules of substance A hit those of substance B.

  14. Larry Ledwick says:

    That is one of the problems with water loop solar heating systems, tanks of hot water become very hard to keep corrosion under control (reason your hot water heater has a glass liner – one of the few thing hot water will not eat through in very short order).

    Same goes for molten metals, molten zinc for example becomes very aggressive and will eat a hole through a thick steel walled vat in just a few days if it gets too hot.
    (worked in a hot dip galvanized wire factory for a while. It was very important to limit the heat of the hot zinc tank to just above its melting temperature to keep all the zinc from running out the bottom of the vat ).

  15. cdquarles says:

    That said, Larry, water will dissolve silica, especially when at supercritical conditions. Think silicic acid.

  16. Larry Ledwick says:

    There is a reason they coined the term “universal solvent” for water. More chemicals / compounds are soluble in water than any other chemical. As noted changing things like temperature, pressure and ph can also make or break those reactions.

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