What is a synonym for "diamond in the rough"?

Common synonyms include: acceptable person, capital fellow, crude, diamond, gem, gentleman.

Diamond in the rough

noun

noun ·Rare ·Advanced level

Noun

1
An uncut diamond.
"He wants to go try his luck at that state park in Arkansas where you can look for diamonds in the rough and you can keep what you find."
2
A person or thing whose goodness or other positive qualities are hidden by a harsh or unremarkable surface appearance. figuratively
"Her auto mechanic is a diamond in the rough: tough-talking but honest, even generous."

"He wants to go try his luck at that state park in Arkansas where you can look for diamonds in the rough and you can keep what you find."