Ask most people what the hardest material on Earth is and they will probably answer “diamond.” Its name comes from the Greek word ἀδάμας (adámas) meaning “unbreakable” or “invincible” and is from where we get the word “adamant.” Diamond’s hardness gives it incredible cutting abilities that—along with its beauty—have kept it in high demand for thousands of years.
Modern scientists have spent decades looking for cheaper, harder and more practical alternatives and every few years the news heralds the creation of a new “world’s hardest material.” But are any of these challengers really up to scratch?
Despite its unique allure, diamond is simply a special form, or “allotrope,” of carbon. There are several allotropes in the carbon family including carbon nanotubes, amorphous carbon, diamond and graphite. All are made up of carbon atoms, but the types of atomic bonds between them differ which gives rise to different material structures and properties.
The outermost shell of each carbon atom has four electrons. In diamond, these electrons are shared with four other carbon atoms to form very strong chemical bonds resulting in an extremely rigid tetrahedral crystal. It is this simple, tightly-bonded arrangement that makes diamond one of the hardest substances on Earth.
How Hard?
