1st off diamonds are made up of carbon. Which despite their hardness is also their biggest flaw. Diamond crystals while hard and sharp atomically, diamonds structurally they are actually brittle.
2nd big fact diamond companies won't tell you is that diamonds ultimate fate is to inevitably end up lead. That's right Diamonds are made up of carbon and what does most carbon based objects do when exposed to natures natural elements when they reach their death point. Or stop growing? They start decaying, yes that precious 1k or 100k usd diamond heirloom family diamond rings ultimate inevitable fate is to end up a chunk of LEAD. >.> While yes in a humans life span diamonds are going to remain a crystal but. In terms of archaeology and the history of a diamond. That 100k+ diamond ultimate fate. Is to end up a chunk of lead. When the carbon dies and decays.
3rd fact sure you can smash a diamond even burn/melt diamonds. But by far the most disturbing way to ruin a diamond or get revenge on your cheating other half dunk it in a vat of LN2 or dry ice and watch it burn faster than you can say OOOPS....
4th Diamonds are like currency they are RELATIVE to what humanity values them at. That means great grandma's ancient ring if diamonds fallout of value they could end up being worthless. Yes that means if culture changes a diamond could end up as valueable as that chunk of quartz you saw outside.