The artifacts discovered at La Venta have been crucial to starting to understand Olmec religion and ideology. For example, hematite and iron-ore mirror fragments have been discovered in abundance at La Venta. Mirrors were an incredibly important part of Olmec society, used in both rituals and daily life. Celts, or "pseudo-axes," are extremely common in both burials and offerings. It is unclear whether these artifacts were actually used in any practical way or if their meaning is ritual or symbolic. Most are smooth, but quite a few are decorated with what has been interpreted as representing religious symbolism. Such celts and other jade artifacts were offered to deities during ceremonies at La Venta and the belief in supernatural beings is evidenced in Olmec artifacts. However, it is difficult to tell which important figures remaining on the stone monuments and artifacts are gods and which are human leaders. In fact, there might have been little difference between the divine and the Olmec king, in their ideology.