hard to tell from the pic
as far as best rock to start on
you will probably get s many differant answeres as there are knappers on that one
i learned on obsidion slabs
i think the best to learn on would actually be
what every is easiest for you to get and is cheapest for you to get
stick with that material untill you get the basics down and you feel comfortable with knapping
then try another material,stick with it untill you gest used to it
if you switch back and forth constalty as you learn,in my opion it makes it harder to learn
each material likes to be workes stightly differantly
some like to be very heavily abraided,some dont
some like a real hard fast switch,others dont
i think some work better with copper and others with antler etrc etc
but wait for othes tochime in as i havde only been knapping a few years now