The diamond industry is facing an identity crisis. Natural diamond prices have tumbled as lab-grown diamonds surge in popularity. Physically and optically identical, they can cost around a tenth as much and can now be produced at mass scale. Their rise is challenging one of the world's most successful marketing stories.Listen to Australian and world news and follow trending topics with SBS News Podcasts.TRANSCRIPTOnce upon a time, a diamond engagement ring was a powerful symbol of social status: the bigger the rock, the greater its cachet.SKIP ADVERTISEMENTToday, ring owners posting on social media will often voice a different sentiment: "Does...