They are very hard to find and they are very very strong. The only thing that can break the gem is another gem of it's kind. They also take tens of thousands of years to form.
No.
Yes, if it is a gem-stone quality diamond.
Depends on the quality of the diamond in question.
Of equal weight, gem-quality diamond is more valuable than silver.
Diamonds are more valuable than coal.
Diamond
yes.
The suspect was believed to have a significant role in the mysterious disappearance of the valuable diamond necklace.
Diamond
no
blue
Brilliant. Valuable. Precious.