Learn Turkish: Safirlerden al, onlar zümrütler gibi çok değerli. - Take some of the sapphires, they are very valuable like the emeralds.

This highlights our current lesson on the partitive ablative case. If you said safirleri al (using the accusative case), it would mean "take all the sapphires." By using the ablative -den ending, safirlerden al literally means "take from the sapphires," which we naturally translate as "take some of the sapphires."

Why do we need the pronoun onlar (they) if Turkish usually drops subjects?

You could technically drop it and just say zümrütler gibi çok değerli, but including onlar adds emphasis. It clearly points back to the sapphires you just mentioned, setting them up for a direct comparison with the emeralds.

Why is zümrütler plural here? Wouldn't zümrüt gibi work?

Zümrüt gibi would mean "like an emerald" or "emerald-like" in a general sense. By using the plural zümrütler gibi, the speaker is referring to a specific group of emeralds that are already known in the context, meaning "like the emeralds."

How is the word değerli formed?

It is built from the noun değer (value or worth). Adding the suffix -li (which means "with" or "having") creates the adjective değerli, meaning "having value" or "valuable."