In "When We First Met", we spotlight the various characters, phrases, objects or events that eventually became notable parts of comic lore, like the first time someone said, "Avengers Assemble!" or the first appearance of Batman's giant penny or the first appearance of Alfred Pennyworth or the first time Spider-Man's face was shown half-Spidey/half-Peter. Stuff like that.
Reader David B. first asked me this one a while back, but then he recently asked again, so, well, let's take a look!
Obviously, Superman crushing some coal into a diamond is an iconic aspect of the Superman mythos. It was so notable that it even made it into the third Superman film...
At the same time, it's not something that would actually work. The Mother Nature Network explained it well here:
Diamonds are essentially pure carbon formed into a crystalline structure. The rarer, colored diamonds do contain minor impurities (boron, for example, makes diamonds blue, while nitrogen turns them yellow), but those impurities exist on a scale of just one atom in a million.
Coal is also mostly carbon, but it is hardly pure. Coal also includes many other substances, including hydrogen, nitrogen, oxygen, sulfur, arsenic, selenium and mercury. Depending on the type of coal and its source, it will also contain various levels of organic materials — coal originates from decaying plants, fungi and even bacteria — as well as moisture. These impurities alone prevent coal from being turned into diamonds. (The impurities are also why burning coal produces greenhouse gases and contributes to acid rain and other environmental problems and why coal mining is so environmentally destructive.)
Beyond that, carbon requires a lot more than pressure to become a diamond. It also requires enormous amounts of heat. In fact, diamonds require a combination of heat (thousands of degrees) and pressure (130,000 atmospheres) that can typically only be found about 90 to 100 miles below the surface of the Earth, deep within the mantle. This heat and pressure work together to allow the carbon to form into the crystalline lattice structure that we know so well. When presented with this heat and pressure, each carbon atom bonds with four other atoms in what is known as a tetrahedral unit. This strong molecular bond provides diamonds with not just their structure but also their classic hardness. That bond would not be possible if impurities were present on anything but a superficial level.
However, whether it is actually feasible or not (which is not really much to say in the world where Superman can, you know, fly so fast that he break the time barrier and travel back in time), the trope popped up all over the time.
When did it first show up, though?