I just heard about pristine solves, acting as quest items to encourage the archaeology grind. From that link, their summary is:
A new type of artifact is added in Mists of Pandaria--pristine solves. These solves are enhanced versions of common-quality solves. Completing them will create a quest item, which can be turned in to the Lorewalkers and displayed in their museum. The chance for creating a pristine version of an artifact instead of a common one is completely random.
Obviously random == "has some percentage chance". Has the chance of a pristine solve been discovered/calculated?