Analyze the color of the wood. The most common types of oak wood for sale are white oak and red oak. White oak will have the appearance of light tan through to darker brown tones, or may be a creamy white color. Red oak is more likely to run the gamut between pink and red.
Look for the unique patterns on oak wood. Oak wood has some of the most distinctive grain patterns of any wood on the market. The grain patterns are generally large and open, and they are a different shade than the base color of the wood, so this creates a unique appearance. Red and white oak both have strong grain patterns, but red oak wood generally has the most visually dramatic.
Feel the density of the wood. Oak is a quality material, and one of the aspects which make it stand out from other woods is the density of the material. Red and white oak are very hard and extremely shock absorbent. A simple knock on the wood with your knuckles should give you an indication as to whether you are holding oak wood; it should sound completely solid and there should be no hollowness to the sound.
Ask an expert. If you are purchasing oak and the materials are not all marked and described, and you are not sure whether you have found oak, ask a worker. It is better to be completely sure you have bought oak rather than finding out at a later date that you have bought an inferior wood.