The first thing you need to see is a natural diamond crystal. This is just a diamond crystal, the way it came out of the ground.
Actually, THIS is what all miners want to find- a perfectly smooth sided diamond crystal called a “glassie.”
I guess someone along the line decided that the diamond would either look good or at least not put the wearer’s eye out if they ground down the point on the top. And they literally did grind down the point. They put the diamond on a wheel covered with diamond dust and (fun fact alert) OLIVE OIL, and simply ground the point down until it created a flat area that looked like a table top. That’s it. That’s how we got table cut diamonds and why they’re called that.
Now you can go forth and impress your friends who are getting engaged with completely useless information about the history of diamond cutting!