Geology, art and mysticism of Tezontle (volcanic scoria) of the Basin of Anáhuac, the newest designated Heritage Stone from Mexico

Abstract

Tezontle from the Anáhuac Basin became Mexico’s second IUGS Heritage Stone in August 2024. This volcanic scoria of basaltic to basaltic-andesitic composition, once considered a ‘providential gift’ or a ‘divine material’, has been used for over twenty centuries in countless architectural monuments, many of which are included in UNESCO’s World Heritage List. The abundant availability of tezontle in central Mexico, combined with its exceptional physical properties of lightness, hardness, and durability, made it the preferred material for building the massive structures of the monumental Pre-Hispanic City of Teotihuacan (1st-7th centuries). Centuries later, the Mexica utilized tezontle to build the island-city of Tenochtitlan (14th-16th centuries), adapting to the challenging lacustrine soil conditions by using it for foundations and masonry. The use of tezontle continued after the conquest of Mexico, adorning numerous New Spain Baroque style buildings (17th-18th centuries) of the center of Mexico City. Both in these buildings, as well as in the later, Neoclassical and functionalist styles structures of the 19th-20th centuries, tezontle was prominently used in façades. Its characteristic dark-reddish hue and rough appearance created a striking aesthetic contrast with the decorative elements of white or gray tufts, contributing to the development of a distinctive architectural identity for Mexico City. Despite the abundance of volcanic cinder cones (source of tezontle) in central Mexico, extensive mining of aggregates around Mexico City has significantly depleted the supply of high-quality stone for producing blocks and tiles. Furthermore, the tradition of artisanal tezontle work has become uncommon.