Unfinished adamant bolts are Adamant bolts before feathers are added. These bolts are made by using an Adamant bar with an anvil, with a hammer in the inventory or tool belt. Each bar makes 10 unfinished bolts, gives 62.5 experience and requires a Smithing level of 73.
These items are commonly made for training the Smithing and Fletching skills due to the high demand for Adamant bolts (including the associated Ruby and Diamond bolts), and the fact that they are stackable and do not weigh anything.
At current Grand Exchange prices, making 10 unfinished bolts out of an Adamant bar will earn the player -208 coins (-3.33 per XP), without bonus experience.