The Badarian culture, from about 4400 to 4000 BC,[50] is named for the Badari site near Der Tasa. It followed the Tasian culture, but was so similar that many consider them one continuous period. The Badarian Culture continued to produce the kind of pottery called Blacktop-ware (albeit much improved in quality) and was assigned Sequence Dating numbers 21 - 29.[48] The primary difference that prevents scholars from merging the two periods is that Badarian sites use copper in addition to stone and are thus chalcolithic settlements, while the Neolithic Tasian sites are still considered Stone Age.[48]