Certain items have additional ways of referencing them if they are the generic type of several different specific varieties. E.g. eggs can be refered to as chicken eggs to differentiate them from goose eggs, duck eggs or quail eggs.
Below is a list of some of these things:
beans - white beans cheese - yellow cheese eggs - chicken eggs iron - wrought iron leather - cow leather sand - beach sand steel - carbon steel sugar - cane sugar thread - plain thread