the type of rock looks workable but those two pieces have quite a bit of fracture in them. those fractures will either break or cause problems for you. where are you located, it will help to identify the rock and other knappers near you. if the stone isnt readily available to you , use glass bottles to start. its a cheap source of material that will teach you a lot and not waste stone. like dana said check out youtube again, theres a lot of info on flintknapping available. two of our favorites are paleomanjim and flintknappingtips. they have videos that will help you get started. peace and happy chippin