<P> Grinding tools are very common at Nok sites . They are rarely preserved in one piece, but can still illustrate the different shapes and sizes of tools used throughout the Nok Culture . Grinding stones were made of quartzite, granitic, or metamorphic rock . At the site of Ungwar Kura, grinding stones seem to have been placed in a certain order, and at the site of Ido huge grinding slabs were arranged in an upright position with pots and stone beads next to them . This context is assumed to have been ritual in some way . Most of the grinders are merely hand - sized . Throughout Nok sites, there is an abundance of grinding slabs but there seems to be a low number of hand stones . It is possible that members of the Nok Culture used these grinders until they reached a certain state of wear, and then repurposed them as pestles . </P> <P> Ground stone axes were another tool commonly used by the Nok . They were typically made from fine - grained volcanic rock (siliceous rock is also sometimes seen), and may have been used in food preparation . These ax blades tend to be smallish in size, the largest reaching 20 centimeters . Stone balls are found at almost every Nok site and are approximately palm - sized . They were probably used as hammerstones or for roughening the surface of a grinding stone . Not all of them are ball shaped, however, and many have chipping marks all over or at least in one place . These stone balls likely would have served as mobile grinding stones . </P> <P> Stone rings have also been found at Nok Culture sites . They are normally found as fragments, but can be identified as rings because of their flat, oval or triangular cross-sections and their shapes . These stone rings are very rare and their purpose is unknown . Another rare find is stone beads, which are typically found as if strung on strings . Beads tend to be carefully made out of hard siliceous rock such as quartz, chalcedony, jasper, or carnelian . There are three different bead shapes: cylindrical, which is the most common shape, as well as rod and ring - shaped . </P> <P> Potsherds are the most abundant archaeological artefacts at Nok sites . Since 2009, excavated pottery has been undergoing systematic analysis with a central aim to try and establish a chronology . Certain attributes of the pottery such as decoration, shape and size appear with an increasing frequency and then disappear being replaced with different pottery attributes . This change can sometime allow one to divide the progression into different intervals based on the different attributes . In total approximately 90,000 potsherds have been collected, and out of that 15,000 have been considered diagnostic meaning that they are decorated, sherds from the rim or the bottom of the vessel, or they have handles or holes in them . The results of the pottery analysis can be delineated into three distinct time periods: Early, Middle, and Late . </P>

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