a diamond pencil的用法和样例：
- She wears a diamond ring on her left hand.
- She wore a diamond clip on her new dress.
- She selected a diamond ring from the collection.
- Having the hardness or luster of a diamond.
- That's not a diamond! If that's a diamond, I'm a Dutchman.
- David produced a diamond ring and asked Dawn if they could name the day.