As they grow, events in nature affect the dividing cells under the bark, resulting in anomalies in grain and color. For examples, the cells and fibers have swirled around a limb or bud, an injury has been healed, pitch or minerals have been deposited in an area--resulting in irregular figure, variable reflectance, iridescence, burls, knots, and dark mineral streaks. When attempting to produce a homogeneous product for a mass market, these natural anomalies are considered defects. We consider them marks of character. When comparing species of wood, we also use the terms below. These refer more to the working and technical properties than the visual and artistic ones.