a rough diamond

diamond in the rough

A person or thing with exceptional qualities or characteristics that cannot be seen from the surface. The new employee initially seemed to lack confidence, but after seeing how hard he works, we realized that he's a diamond in the rough and is really a great asset to the company.
See also: diamond, rough

rough diamond

Someone or something that is unrefined but has many exceptional aspects or underlying potential. Primarily heard in UK, Australia. The young actor was a rough diamond. With some training, she'd become a superstar.
See also: diamond, rough

a rough diamond

mainly BRITISH or

a diamond in the rough

AMERICAN
1. If you call someone, especially a man a rough diamond, you admire their good qualities, even though they are not very polite or well-educated. Note: A rough diamond is a diamond that has not yet been cut and polished. Marden was the rough diamond of the three, feared for his ruthlessness but respected for his First World War Military Cross. I liked Neil Murphy, who is somewhat of a diamond in the rough.
2. If you call someone or something a rough diamond, you mean that they have talent or good qualities which are hidden or not well developed and could be developed more. Note: A rough diamond is a diamond that has not yet been cut and polished. British first novels are more likely to be rough diamonds, with flashes of inspiration in an imperfect whole. When I heard this lady sing, I ran to the theater, and I said, `Chick, I found myself a diamond in the rough.'
See also: diamond, rough
References in classic literature ?
He's not a rough diamond - a pearl-containing oyster of a rustic: he's a fierce, pitiless, wolfish man.
His awe for the mysteries of nature prompted him to get the attention of consumers this holiday season by giving a rough diamond to each client with their purchase of a finished "rock.
There are about five experts in the world that could look at a rough diamond and tell you where it came from.
IDH Diamonds NV, which has extensive experience as a rough diamond dealer and has demonstrated the skills to bring new production to market, will continue to provide consulting services to the sales office.