Diamond is the Hardest Natural Substance myth

What is the Hardest Natural Substance on Earth

Diamond is the most common of the naturally occurring “hardest” substances, but Q-carbon, wurtzite BN, lonsdaleite, ultrahard fullerene, graphene, and carbyne are all harder.^{[1][2][3][4][5][6]}

Which Substances are the Hardest?

Substances harder than diamond, though typically only synthesized, can also occur naturally.

Generally, it is the carbon molecule, not the diamond itself, which seems to have the distinctive “hardness” property.

All of the hardest substances aside from wurtzite BN are carbon based.

Diamond is certainly the most common of these to naturally occur on earth by a long shot, meanwhile lonsdaleite comes from meteorites crashing into earth, wurtzite BN can be produced in volcanic eruptions, graphene is found in graphite, and all have been synthesized in a lab in using pressure, heat, and lasers.

Typically diamond is also the most stable and usable of the aforementioned as of December 2015, and thus we can say “diamond is the hardest of the common naturally occurring substances, but other less common naturally occurring carbon based substances such as wurtzite BN, lonsdaleite, and graphene, are harder.”

Let’s look at each substance and figure out if it counts as a natural substance, if we found it on earth, if it naturally occurs, and if it’s harder than diamond.

TIP: Generally, these hard substances are used to create “hard” materials like kevlar (i.e. kevlar is a “hardest material” not a “hardest substance”.)

FACT: A correct way to phrase diamond’s status of hardness would be “Diamond is the hardest naturally occurring non-rare substance on earth that doesn’t require synthesis”.

Carbon allotropes and compound images. Pretty cool how central geometry is to the universe, right?

Which Substance is the Hardest Natural Substance?

All of the following substances have been shown to occur naturally (although many require an impact from a meteorite, synthesis, or have only been theoretically shown to occur). This list is not necessarily exhaustive since new discoveries are made every day.

• Diamond. It’s a natural substance made from carbon atoms and we have found it occurring on earth. Synthetic diamond can be produced from graphite (graphite is also made of carbon, but oddly is one of the softer substances.
• Q-carbon. Q-carbon is made from carbon just like Diamond, but it hasn’t been found. Instead, it can be created in a lab. It can be created in a lab by concentrating a very short pulse of laser light onto carbon. It’s harder than diamond.^[2]
• Graphene. Graphene is made from carbon and is found in graphite. It must be synthesized from graphite to be useable. It’s stronger than diamond.
• Carbyne. Harder than diamond or graphene. Found in graphite, but also occurs in meteors.^[7]
• Wurtzite boron nitride (AKA Wurtzite BN). Boron nitride on its own is softer than diamond, but its thermal and chemical stability is superior. Scientists synthesized some in a lab, but it wasn’t stable. This substance can occur naturally, but requires events like massive meteorites impacting earth or volcanic eruptions, which produce very high temperatures and pressures. It’s harder than diamond.^[4]
• Lonsdaleite. Sounds like a horse, and it’s harder than a rock (58% harder than diamond). It’s carbon based just like a diamond and can occur naturally. The mineral is naturally occurring only  when meteorites containing graphite hit Earth.^[4]
• Ultrahard Fullerite. Fullerite is made of buckyballs or fullerenes, named after futurist Buckminster Fuller, due to the sphere-like shape the carbon molecules take. Ultrahard Fullerite can be synthesized from fullerite by using ultra-high pressure (HPHT) processing. It’s also harder than diamond.