What did Mihawk teach Zoro?

I do think Mihawk taught Zoro the basics of haki as seen when he is telling Zoro about any sword becoming the black blade. What do you guys think ? Mihawk simply made Zoro aware of the existence of Haki, then he left him alone with the copy cat Gorillas.

Did Mihawk train Zoro to Haki?

Mihawk is an expert Busoshoku Haki user. He taught Zoro how to use Busoshoku Haki to protect his swords from any damage.