The word diamond derives from the Greek word ‘adamas,’ meaning indomitable and invincible, a fitting name for the hardest natural substance on earth. This is also similar to the Latin verb ‘adamare’ — to love passionately. The Greeks believed diamonds were the tears of the gods, and Romans thought they were shards from the stars. Many stars have diamond cores. The biggest known diamond in the universe weighs 2.27 thousand trillion tonnes, or 10 billion trillion carats. This is the equivalent of 179 trillion double-decker buses. Diamonds are formed deep within the Earth, under intense heat and pressure and pushed to the surface at incredible speeds in upsurges of volcanic molten lava. Diamonds were formed long before dinosaurs roamed the Earth, and some are even older than the stars. The youngest diamond is nearly a billion years old. Diamonds are the hardest natural substance known to humankind. They are 58 times harder than the next hardest mineral on Earth. The only substance that can scratch a diamond is another diamond. A diamond over one carat in weight is one in a million. Diamonds are extremely rare. If you were to gather together all the diamonds ever polished since the beginning of time, they would fill only one double-decker bus.