A diamond is forever

I did have more weird dreams last night, but this actually happened...

T: So, say we'd been dating for three years and I was going to do the whole "getting down on one knee, asking you to marry me" thing. How would you feel if I'd gotten the diamond from a friend of mine who used it to propose to his girlfriend?
A: I'm trying to be rational. The consumer part of me knows that it shouldn't matter but the sentimental part of me is not okay with that. Don't do it.
T: Even if it is just the diamond and not the ring.
A: Nope--don't do it.
T: So girls just want us to spend more money on them.
A: No, we just want our ring to representative of our unique relationship and it doesn't feel like it is unique if the diamond was already given to another girl.
T: But the diamond has already been around a long time. They take a long time to be formed.
A: Still.
T: But what if a jeweler sold you a ring that had been given to someone else.
A: If I didn't know it would be okay.
T: So a third party "sanitizes" it?
A: No, it is just okay if I don't know.
T: Would it be okay if I bought it off eBay and you didn't know whose ring it had been?
A: No. Besides, girls have specific preferences about what they want. You know--what style, white gold, yellow gold, platinum. Personally I want yellow gold.
T: Yeah, but it's a diamond.
A: But girls are going to want a specific cut--marquis, princess, pear-shaped, emerald.
(Silence)
A: A pear-shaped diamond is rounded at one end and tapers to a point at the other--they make your fingers look long and slender. Emerald cut is rectangular...
T: I'm a guy--I don't care about diamonds. I think the whole "buy a girl something expensive that has the potential to cut things" is dumb.