I bought two nodules from Dixie several years ago. I had intended to try some knapping, but, as with many of my grand schemes, nothing came of it. There they sit.
You'll get a lot of material with the raw nodules from Dixie, although I expect a lot of it will end up as waste. I will say, their nodules appear to be the "real deal," black flint in large, irregularly shaped lumps partially covered with white chalk.
I still haven't learned to knap, but after researching it some years ago, I uncovered a few resources. You
might be better off getting some spalls or shards already broken off the nodule. I would suggest
www.goknapping.com as a resource. I've ordered a few odds and ends from them a couple of times. It's a small, family operation with fast response and good customer service. One time, they enclosed a beautifully knapped finished projectile point with my order, as a "thank you" gift.
Good luck with your endeavour!
Notchy Bob