German chemist Tributsch (2017) proposed pyrite mud with plant juice etched volcanic, silica-rich rock into silicate glue, while crushed pyrite generated hot sulfuric acid. Garcilaso called the reddish mortar 'alpacalpa.' Note: per the paper, applies to silica-containing volcanic masonry. Still speculative.
Tributsch pyrite paste theory explains Inca megalithic block fitting
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Key facts
- German physical chemist Helmut Tributsch published a 2017 article in the Journal of Earth Sciences and Environmental Studies on the reddish glittery mud the Inca used for stonemasonry.
- Acidic pyrite mud (pH around 0.5) combined with plant juice containing oxalic, oxalic, and citric acids could etch the surface layer of Jurassic limestone, turning it into a thick silicate glue.
- Pure crushed pyrite added to the mixture initiated a vigorous exothermic reaction, generating hot sulfuric acid in the gap between heavy blocks that dissolved rock further.
- Garcilaso de la Vega described the Inca mortar as a reddish sticky clay called alpacalpa; chroniclers Cieza de León and Diego de Aguja also confirmed its use.
- The theory applies specifically to carbonate rocks like the Jurassic limestone at Sacsayhuamán but cannot account for the granite at Machu Picchu or andesite in central Cusco.
- British explorer Percy Fawcett recorded in his early 20th-century diaries observations of an indigenous bird (pito or hakllaw) using plant juices to soften rock for nesting.
Sources
repositorio.cultura.gob.pe
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On the reddish, glittery mud the Inca used for perfecting ...academia.edu
Inca builders utilized highly acidic mud (pH = 0.5) from pyrite oxidation for masonry techniques. Acid mud accelerated softening of volcanic rocks,
Machu Picchu and Mysterious “Gold” Mortarroseannechambers.com
Published in 2017 by a European chemist, Helmut Tributsch, the title captures the essence of his work: “On the reddish, glittery mud the Inca ...
On the reddish, glittery mud the Inca used for perfecting ...semanticscholar.org
Tributsch et al. mud the Inca used for perfecting their stone masonry ・ s Published 30 December 2017 Engineering ・ performance-based dry masonry construction
Inca Red Clay used for perfecting their stone masonryforum.rocktumblinghobby.com
H. Tributsch Due to its impressive appearance, Inca masonry, which mostly consists of volcanic, silica containing rock material, has received much attention ...
On the reddish, glittery mud the Inca used for perfecting ...scispace.com
On the reddish, glittery mud the Inca used for perfecting their stone masonry · Fabrication Methods of the Polygonal Masonry of Large Tightly-fitted Stone Blocks ...
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