A basic sorting system was assembled, composed by a few hoppers with rails on top.
A minecart w/chest made the duty of distributing the items along the line, The hoppers placed items in minecarts below to distribute the items into organized chests.

The problem occurs when the minecart above the hopper brings in Leather (Tried with Redstone torches and Gold Ore). The hopper won't retrieve the corresponding items from the minecart, and won't deploy them into the minecart below either.