Diamonds are not that rare. They're durable, so it's not like an old diamond is going to break or something. So, there should be plenty of diamonds for everyone who wants one. Rings made in the 1920s and up probably have some sort of diamond in it, and if you don't like the ring, keep the gem and craft a new ring around it. I prefer more rare stones, such as a padparadscha sapphire, or Alexandrite. I prefer to give my woman a gemstone as rare as she is, and as colorful as she is, not something which has virtually no color, and is definitely not rare.
You obviously haven’t seen the video of a diamond being hit by a hammer against a steel anvil…and it was fine, even putting a dent into the anvil. You have to cleave it in just the right spot to split it - blunt force isn’t going to do it.
Mild steel like that in an anvil is far from the hardest material you'll encounter in daily life. If you hit a diamond between two hammers, which are made of far harder and tougher tool steel, it will easily shatter and pulverize, no finesse required. See : https://www.youtube.com/watch?v=l0EXgYA7ve8 for an example.
The reason why on an anvil you need to orient the diamond carefully to break is just because the tip needs to be facing some kind of reasonably hard material like tool steel, if it's being driven into mild steel, that will basically just act as a pillow for the diamond and allow the flat face to align parallel to the surface of hammer, minimizing the impact.
