heart of glass

By metaphor, from the notion that glass is fragile (easily broken).

• (Received Pronunciation) IPA^(key): /ˌhɑːt ə ˈɡlɑːs/
• (General American) IPA^(key): /ˌhɑɹt ə ˈɡlæs/

• Audio (General Australian):

  (file)

heart of glass (plural hearts of glass)

1. (idiomatic, figurative) A heart (or by extension, person) in a very fragile romantic state: one that is easily made broken-hearted.
   • 1978, Debbie Harry, Chris Stein, “Heart of Glass”, in Parallel Lines, performed by Blondie:

     Once I had a love and it was a gas / Soon turned out, had a heart of glass

   • 1986, “West End Girls”, in Please, performed by Pet Shop Boys:

     You've got a heart of glass or a heart of stone / Just you wait 'til I get you home

• heartbreak
• glass-hearted

• heart of gold, heart of stone