Raw diamonds are uncut and unpolished. In general a raw diamond is what you will see directly from a diamond mine before it is sent to a jeweler to be processed and put into a piece of jewelry. Identifying raw diamonds can best be done by the trained eye, such as a professional jeweler. But, there are a few characteristics that a novice can look for to determine a natural, raw diamond.
View the shape of the "diamond." Rough diamonds come in a few different shapes. These shapes are the octahedra, cubic and macle. The octahedra is the most common shape and looks like two pyramids joined together at their bases. The cube shape is a six-sided box structure. The macle is half of an octahedra. Rarely a raw diamond will be a dodecahedron. The dodecahedron is round and has many flat surfaces. If a raw diamond is a dodecahedron, it will be distorted version.
Look at the surface texture of the diamond. Raw diamonds have a few possible surface textures. These textures are mirror or glass-like, frosted or water worn and grooved or serrated. The glass surface will provide some transparency. The frosted surface will be cloudy and is commonly found on diamonds that are found near river beds. The grooved surface will have a wavy or step-like texture.
View the diamond under a magnifying glass or a jewelers loupe and look for inclusion. Each raw diamond has inclusions. These are flaws inside of the diamond and can appear as cracks that run through the interior of the diamond, hollow areas or spots of other minerals that formed within the diamond. Many times inclusions are available to the naked eye. Even a heavily included diamond can be valuable.