I finished up a dagger today from a slab of flint / chert that was given to me and I do not know what type it is. It is raw with some small crystal pockets. It worked well and is nice and hard. Since the slab was rather thin for its size, I only used indirect (Jack Crafty style) and pressure. The blade ended up to be 5 1/2 inch long and I added a Walnut handle for a overall length of 9 1/2 inch long.
I think I will keep this one.