Cassia is an evergreen tree with an aromatic bark, similar to cinnamon, but darker, thicker and coarser. The outer surface is rough and greyish-brown, the inside bark is smoother and reddish-brown. The stems are cut down when the bark is mature. The bark is removed in short lengths and dried, then ground into powder or rolled from both sides toward the center, to form a quill resembling a scroll. An aromatic oil can be derived through steam distillation of the leaves to produce a strong and penetrating fragrance.