Normally they don't know because they're getting it from some other source. Occasionally they just don't want to say. 'Where did you get this?' is not the sort of information that dealers normally give up easilly whether we're talking about diamonds or anything else. As you point out, nearly every diamond ever mined is still out there and they change hands at least every generation or so. A stone examined by a lab yesterday could quite possibly have been mined 100 years ago. 'Used' is a slightly odd concept when it comes to rocks.kenny|1350671236|3288709 said:Could be either.
BTW a report dated yesterday does not mean a diamond was never owned/worn by 10 previous customers.
After divorce or death people do not throw away diamonds.
Some get sold, re-polished if needed, and re-enter the retail market.
I've bought a lot of diamonds and often question vendors on the diamond's history, but get no information.