also depict obsidian. Typically, the material's visual depiction in artwork is generally associated with autosacrifice and other types of sacrifice, including images of prismatic blades with bloody hearts on the blade's ends. Unfortunately, the majority of the material record is out of context yet the implications and interpretations that are drawn from artwork are substantial and reflect a corpus of beliefs and ideology involving obsidian. Some of the more significant portrayals of obsidian use involve blood-letting and warfare. One example includes the macuahuitl, a broad–faced club studded along its edges by obsidian prismatic blades. These weapons are predominantly used in ritual warfare and generally date to the Postclassic period. Earlier depictions of obsidian is usually restricted to their appearance as razors or lancets, and it is commonly believed that the material was not associated with weapons such as clubs or spears until later phases in Mesoamerica. In the Aztec writing system, a curved prismatic blade represents the phonetic value itz (Taube 1991) and results in the term itztli, as mentioned. Value Obsidian was widely distributed throughout Mesoamerica by trade. Its importance to Mesoamerican societies has been compared to the value and importance of steel to modern civilization. However, archaeology provides varied evidence of the individual value placed on obsidian. For example, during the Preclassic period, obsidian was a rare item in the lowland areas, found predominantly in high-status and ritual contexts. In many Maya excavations evidence of obsidian is likewise found most frequently in privileged settings. As the Late Classic period progressed, obsidian became increasingly accessible to the lower classes of Maya civilization. Nevertheless, the Maya upper classes continued to remain in possession of the more prestigious Teotihuacan green obsidian. In the Teotihuacan culture obsidian was perhaps traded at a loss of human effort in transport across long distances. The profit from the trade lay in prestigious high-status items received in return. Obsidian has both been seen as a key element to Teotihuacan's rise to power and as a side trade element that simply augmented their already developing wealth. Obsidian forms part of many high-status items, such as valuable ear-spools, but these obsidian ear-spools have also been discovered in exclusively lower-status settings. Thus the value of obsidian can be considered highly variable. It was an important trade item, but is found in a variety of environments, unlike many items whose ownership was confined to the upper classes. Finally, there is