From the looks of it, Jack, what you got there is an onion burl. These are different from the oak, maple, and cherry burls that you see, which are pin burls. Just from the name, you can probably guess the difference. Just in case, the pin burls are made up of a mass of individual growths shaped like, you guessed it, pins. if you cut off the top, it will look like a bunch of small circles all mushed together. An onion burl is made up of, yup, layers like an onion. It's basically where the tissue of the tree grew rapidly in one spot and a cross section will look alot like an onion cut in half.
This makes a difference when turning how? Well, you want to pay a bit more attention to the grain orientation with the onion burl. With pin burls, pretty much anywhere you cut will be highly figured with flame patterns. You're less likely to get flame like figure but more likely to get big swirls and streaks in the onion burls so check your figure often when cutting. Also, orientation of the stock matters more, as you have the option to turn out the inside to pursue having one or two layers of grain be the whole bowl.
Have fun,
Dietrich
