Diamonds are "measured" in CARATS first of all. Usually 1 gram is equivalent to 5 carats. And a 5 carat diamond can be worth between $100 - $100k depending on color, quality, clarity etc.
I really don't see how you can call this "STABLE".
Talking about "backed by diamonds" ... how many grams do you have to back your coin?

Value is that of a 1 gram (5 carat), UNCUT diamond, which is around 100$. So far i have 50 grams of diamond.
Thank you for your opinion.