Life's Little Mysteries

Can diamonds burn?

If diamonds can burn, are they really "forever"?
If diamonds can burn, are they really "forever"? (Image credit: Shutterstock)

Diamonds are forever, or so the slogan goes. But with the proper application of heat and enough oxygen, a diamond can go up in smoke.

Diamonds are carbon, just like coal. It takes a bit more to get them burning and keep them burning than coal, but they will burn, as numerous YouTube demonstrations will attest. The trick is to create the right conditions so that a solid diamond can react with the oxygen required to fuel a fire.

"You have to convert that solid [carbon] into a gas form, so it can react with the air to make a flame," said Rick Sachleben, a retired chemist and member of the American Chemical Society.

Related: Which is rarer: Gold or diamonds?

The best way to do that? Heat — and lots of it. In room temperature air, diamonds ignite at around 1,652 degrees Fahrenheit (900 degrees Celsius), according to West Texas A&M University physicist Christopher Baird. For comparison, a high-volatile coal (coal containing a relatively high amount of easily released gases) ignites at about 1,233 F (667 C), whereas wood ignites at 572 F (300 C) or less, depending on the type.

When first heated, a diamond will glow red, then white. The heat enables a reaction between the surface of the diamond and the air, converting the carbon to the colorless and odorless gas carbon monoxide (a carbon atom plus an oxygen atom).

"The carbon plus the oxygen to make carbon monoxide generates heat; the carbon monoxide reacting with the oxygen generates more heat; the rising heat causes the carbon monoxide to move away, so more oxygen is brought in," he told Live Science.

That fire, however, will amount to only a glow. Nurturing a flame on the surface of a diamond usually requires an extra boost: 100% oxygen rather than room air, which is only 22% oxygen. This increase in concentration gives the reaction all that it needs to self-perpetuate. The carbon monoxide rising from the diamond ignites in the presence of oxygen, creating a fire that seems to dance on the stone's surface.

"Almost everything burns incredibly in pure oxygen," Sachleben said.

Even without pure oxygen, diamonds can be damaged by flame, according to the Gemological Institute of America (GIA). Typically, a diamond caught in a house fire or by an overzealous jeweler's torch will not go up in smoke, but instead will combust on the surface enough to look cloudy and white. Cutting away the burnt portions will reveal a smaller, but once again crystal-clear, stone, according to the GIA.

When carbon burns in oxygen, that reaction produces carbon dioxide and water. A pure carbon diamond could thus theoretically vanish entirely if burned for long enough; however, most diamonds do have at least some impurities like nitrogen, so the reaction is unlikely to be quite that simple. 

Originally published on Live Science.

Stephanie Pappas
Live Science Contributor

Stephanie Pappas is a contributing writer for Live Science, covering topics ranging from geoscience to archaeology to the human brain and behavior. She was previously a senior writer for Live Science but is now a freelancer based in Denver, Colorado, and regularly contributes to Scientific American and The Monitor, the monthly magazine of the American Psychological Association. Stephanie received a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz. 

  • Ben
    "... When carbon burns in oxygen, that reaction produces carbon dioxide and water.."
    'Water'? That would be interesting. With just carbon and oxygen present, where did the hydrogen necessary for water come about?
  • JeetsN123
    I once saw a Youtube video where a guy burned diamonds, captured the CO2, and then used it to make carbonated water in a Sodastream! It's a very fun video.
  • Chem721
    Ben said:
    With just carbon and oxygen present, where did the hydrogen necessary for water come about?

    Technically, with a diamond, wouldn't the very terminal carbons of the carbon-matrix which are in contact with atmosphere contain a hydrogen atom, as the carbon-carbon tetrahedral structure must end at that point? Either that, or perhaps a hydroxyl group. Hydrogen sounds most likely. Certainly would only produce an ultra-trace of water, but an ultra-trace is not nothing!

    More importantly, as I think of "ideal" diamonds being a crystal of pure carbon, each atom in sp3 orbital links to four others, if it is pure and without cracks, aren't you looking at a single molecule of carbon, since all of it is covalently bonded? This is the ideal of course. Inclusions muck up the notion, but not if they are trapped and there are no surface-to-surface cracks in the diamond, it seems like each could be a single "molecule" of carbon.

  • McRa1e
    I am also having this question in my mind MyBalanceNow.
  • Uncle Al
    Diamond is s stable to 1000 °C in air, 1500 °C in inert or reducing atmosphere. No glow to ~1000 °C re Debye temperature. If you drop a really hot diamond into liquid oxygen, it skittles around burning.

    However, in contact with carbiding metals, diamond catalyticaily decomposes to graphite at room temperature, If you put some diamond dust on your finger and draw ia across molybdenum, you can see the immediate darker grey streak from molybdenum carbide.

    A poorly cut diamond will cleave into thin triangles with hardly more than a brisk tap.
  • Reeii Education
    Yes, diamond can be burned. The most common form of burning in everyday life is carbon combustion. In carbon combustion, carbon atoms break their bonds with each other and with other atoms (which requires energy) to form bonds with oxygen atoms (which releases even more energy than first required). The net extra energy released in this reaction can then go on to rip more carbon atoms free of their non-oxygen neighbors, thus continuing the reaction, or the energy can escape as heat and light. Carbon bonded with oxygen makes carbon dioxide and carbon monoxide, which are the waste products of combustion. They drift away from the fire as gases. Since biological organisms, and the fuels derived from biological organisms, contain a lot of carbon, much of the burning that goes on around us is carbon combustion. This includes camp fires, candles, car engines, and gas stoves. Pure diamond consists only of carbon atoms bonded into a dense, strong crystal lattice, so diamond can also undergo carbon combustion. In fact, Antoine Lavoisier first determined that diamond is made out of carbon by burning it and showing that the combustion product was carbon dioxide. The book Diamond Films and Coatings by Robert Foster Davis states, "In 1772 the French chemist Antoine L. Lavoisier found that the products of diamond combustion behaved as, and most assuredly were, solely carbon dioxide... He determined that the ignition and burning of each produced equal amounts of ‘bound air'."
  • sarajo
    Thanks for the science lesson - appreciate that youve given me some great help with my science homework .
  • Uncle Al
    Heat a diamond to about 800 °C and immediately drop it into liquid oxygen. Shhhhhoooosh.

    Diamond does not glow even at 1000°C - Debye temperature.
  • sarajo

    I can add that to my notes for my homework -appreciate that
  • Uncle Al
    tYyd29-gtpAView:… diamane

    Pull your thumb out and add something of your own effort. Put some flesh in the game - lonsdaleite.