In the past, one of the most common techniques to test if a diamond was real or synthetic was to scratch the gem against glass — if the glass is scraped or scratched, the diamond's real. But this ...

New York Times subscribers* enjoy full access to TimesMachine—view over 150 years of New York Times journalism, as it originally appeared. *Does not include Games-only or Cooking-only subscribers.

Exploring a home science experiment where carbon is transformed into a diamond and then tested in a real-world break test, ...