expression, noun
a jewel in a dunghill
Idiomatic expression meaning something beautiful or outstanding in a shabby or unworthy place; often used to describe a person who seems out of place in a lowly environment.
あの田舎の学校に彼のような天才がいるなんて、掃き溜めに鶴だ。
Having a genius like him in that rural school is like a jewel in a dunghill.
The expression literally means 'a crane in a rubbish heap,' evoking the image of a graceful crane among trash. The exact origin is uncertain, but it is a traditional Japanese idiom.