1 oz. (28 grams) White Oak Bark Powder Wild Crafted (Quercus alba) Also known as Quercus alba or Quercus robur, and oak bark. Introduction The oak's botanical name quercus comes from the Celtic words quer (fine) and cuez (tree). Constituents Starch, tannins, resins, calcium oxalate, quillaic acid. Parts Used Dried or toasted bark. Gentle dry heat increases the concentration of volatile oils in the bark. Bark, ground before storage. Gentle heating concentrates healing volatile oils in oak bark pieces, but destroys volatile oils in oak bark once it has been powdered.