Can a person buy diamonds as an investment?

It's well-known that a private individual can invest in precious metals such as gold and silver,either through account backed by the metals or buy purchasing it and physically keeping it in their possession.Can a person do the same with diamonds?I don't mean buying a necklace made of them for cosmetic purposes (although I understand that would have monetary value );I mean buying literally diamonds that you can keep and store like gold,silver,etc.