tezontli.

See also tetzontli, which is a foundation (probably originally involving this kind of stone). We are taking Karttunen's lead here, separating tezontli from tetzontli, although in various sources the distinction becomes blurry (e.g. Hubert Howe Bancroft or Alexander von Humboldt).

"Occuring in 1.4 percent of the burials that include artifacts, tezontli is a relatively rare material in burial offerings...."
Martha Lou Sempowski, Mortuary Practices and Skeletal Remains at Teotihuacán (Salt Lake City: University of Utah Press, 1994), 158.

"Tezontli is the local term for very spongy volcanic rock that occurs in a wide variety of sizes that was used from Tlamimilolpa ceramic phase through the Metepec phase for subflooring, for fill, and cut into facing stone for walls."
The Teotihuacan Valley Project Final Report: The Toltec Period of the Valley (Department of Anthropology, Pennsylvania State University, 1987), 708.

"Architects and sculptors used for preference the jade called nephrite, in the Aztec language quetzaliztli, and the petrified red blood of the porous tezontli; the armorers worked with the itztli, obsidian, in making knives, swords and clubs."
Fernando Benítez, In the Footsteps of Cortés (London: Peter Owen, Ltd., 1957), 203.