કાળા પણ હાથ સોનાના છે.

kāḷā paṇa hātha sōnānā chē.

Literally: They are black, but their hands are of gold.
What it means: A person may look unappealing or be of low status, but they are highly skilled or productive.

Also said as

ગુજરાતી કહેવતસંગ્રહ (Gujarati Kahevat Sangrah) (1923) · read from the scan by machine — the Gujarati itself is unchecked · English is machine-made and nobody has checked it yet

Heard it differently, or know we've got the sense wrong? Tell us — that is exactly the kind of correction this needs.