chalk and cheese

Etymology
Attested in variant form since 1393. The surface of some cheeses, particularly unaged ones, looks similar to chalk – white, crumbling – but in substance cheese is much softer than chalk.

Interesting to note that lime chalk and cottage cheese forms a glue-like material used in the restoration of ancient half-timbered houses, perhaps suggesting an alternative original meaning.

Translations

 * Arabic:
 * Chinese:
 * Mandarin:
 * Dutch: het verschil van dag en nacht
 * Finnish: yö ja päivä
 * French: le jour et la nuit
 * German: Äpfel und Birnen,  wie Tag und Nacht
 * Japanese: 月とスッピン
 * Polish: powierzchownie podobny
 * Russian:, не́бо от земли́
 * Spanish: parecerse como un huevo a una castaña, como agua y aceite, día y noche
 * Urdu: زمین اور آسمان