On my phone so rather short answer but it's an easy question to answer : stone! The same materials that, in most cases, Europeans and Asians used before mastering iron and other hard metals.

While obsidian is arguably the most famous example of mesoamerican knife and tool work they were not as commonly used as more easily available stone or sometimes even bronze knives and tools.

Most commonly, despite bronze being consistently produced, most agricultural tools were made either out of stone (sharpened in the case of shears) or hard wood due to a combination of poor quality and the importance of rare metals as a status symbols, which contributed to their exclusive use by the elite classes. Almost all the finds in modern museums of metalwork from the Incas are knives, swords or other symbolic weapons/pendants/medical tools, commonly referred to as 'tumi' - out of which the ceremonial half moon shaped knives are probably the most well known.

http://www.jstor.org/discover/10.2307/3104667?sid=21105867172393&uid=4&uid=3739448&uid=2&uid=3737720 http://www.discover-peru.org/tumi-knife-culture/