Complex sentence: Copper ores were mined on a large scale at sites like Rudna Glava, but only a fraction were smelted and cast into metal artefacts--and these were ornaments and trinkets rather than functional tools, which continued to be made from chipped stone, bone and antler.
Split into simpler sentences: Copper ores were mined on a large scale at sites like Rudna Glava, but only a fraction were smelted and cast into metal artefacts. Invariably these were ornaments and trinkets rather than functional items; tools continued to be made from chipped stone, bone and antler.