The Types of Walnut for Gunstocks: A Complete Look

If you've spent any amount of time looking at stock blanks, you will know that there is no such thing as "just walnut." French, English, Black, Bastogne, Turkish, Italian, and Claro are all names you will see pop up. So what's the difference? What is Claro Walnut? Is there a difference between Turkish and Circassian?