This paper presents a functional study of lithic tuff tools from the Tu-54 site, a ceremonial settlement from the early Formative period (ca. 3500 - 1500 cal. BP) located in Quebrada Tul??n, at the southern end of the Salar de Atacama basin. The tuff in Quebrada Tul??n is found in large quarries which were intensively exploited for the production of blade tools that were transported and used at the site. We sought to understand the function and effective use of these instruments by analyzing their use-wear traces. We devised and applied a program of experimentation and analysis of the pieces by means of low and high magnification optical microscopy, contrasting our observations with those made of a tool sample from the site. The results show a wide variety of functions and uses for the tuff instruments at the Tul??n-54 site, including some unsuspected ones, allowing for a better understanding of the role of this raw material in the activities undertaken at this early ceremonial settlement.