Fig.: a person of great potential, but lacking training or polish. Someone unsophisticated in his/her manners and appearance, but who is usually a very nice and kind person

Laura is a rough diamond, but she's the only relative of mine who offered to help me when I was struggling

Laura sarà anche un po' grezza, ma è stata l'unica mia parente che si è offerta di aiutarmi quando ero in difficoltà

She's very talented, her singing voice is beautiful, but she's still a diamond in the rough: she needs help with her acting, her gestures and stage presence

Ha molto talento e ha una voce bellissima, ma è ancora un diamante grezzo: ha bisogno di migliorare la gestualità, la recitazione e la presenza scenica

Term from the mining industry. The uncut, unpolished diamond may look like a worthless rock but, after it is cut and polished, it could be both beautiful and very valuable. The first recorded use in print is in John Fletcher's A Wife for a Month, 1624: "She is very honest, and will be as hard to cut as a rough diamond"