Physicochemical Study of Black Pigments in Prehistoric Paints from Oxtotitlán Cave, Guerrero, Mexico

Strategies for14C Dating the Oxtotitlán Cave Paintings, Guerrero, Mexico

“…ESEM images of cross-sectioned samples further demonstrated that the natural coating is heterogeneous with a mixture of microcrystals and platy crystals. The morphologies and elemental concentrations are consistent with whewellite and/or weddellite for the microcrystals, while the platy crystals, along with the presence of sulfur, indicates gypsum (CaSO 4 ·2H 2 O) (McPeak et al 2013; Russ et al 1999). Optical microscopy of polished thin-sections revealed that the thickness of the oxalate/sulfate rock coating was ~ .5 mm and completely covers the paint layers.…”

“…Results of these analyses showed elevated iron for red paints and elevated copper for green paints, compared to the background. Nevertheless, manganese and iron concentrations in all black paintings at the site measured below the detection limit of the instrument or were statistically the same as the background compositions, i.e., ≤ .014 ± .004 % (McPeak et al 2013). This fact is in contrast to analyses of black paints in the Lower Pecos Canyonlands, Texas, where measured concentrations of manganese in black paintings were consistently and significantly greater than ambient concentrations (Koenig et al 2014).…”

Chemical characterization and radiocarbon dating of the rock art of Las Charcas caves, Cuba

“…Preliminary studies of the black paint from the Oxtotitlán cave paintings near Guerrerro, Mexico, showed that the paint was a pyrolytic carbon, likely soot or finely divided charcoal, indicating that the primary mural would make a good candidate for PCO and AMS radiocarbon dating (McPeak et al . 2013). Upon further study, however, the pigment was determined to be bitumen, making the Oxtotitlán mural the first finding of chapapote in prehistoric rock art (Russ et al .…”

Thermally-induced color transformation of hematite: insight into the prehistoric natural pigment preparation

“…These types of iron minerals in ochres produce a range of colors, from yellow, α-FeOOH—goethite ( Longa-Avello et al., 2017 ; Mondragón et al., 2019 ; Salomon et al., 2012 ), brown, -Fe 2 O 3 —maghemite ( Cornell and Schwertmann, 2003 ), red, α-Fe 2 O 3 —hematite, and purple, α-Fe 2 O 3 —hematite or KFe 3 (SO 4 ) 2 (OH) 6 —jarosite ( Hunt et al., 2016 ; Huntley et al., 2015 ; Ilmi et al., 2020 ; Kurniawan et al., 2019 ; Nurdini et al., 2020 ). In addition, other colors in rock art images, such as black, contain manganese oxide or charcoal ( McPeak et al., 2013 ; Chalmin et al., 2003 , 2004 , 2006 ), while white contains Al 2 O 3 2SiO 2 ·2H 2 O—kaolinite, Mg 3 Ca(CO 3 ) 4 —huntite ( Huntley et al., 2014 ), CaSO 4 .2H 2 O—gypsum or CaCO 3 —calcite ( Ilmi et al., 2021a ). Among all the natural minerals that have been mentioned, red ochre, which contains hematite, is the most widely used natural material as a pigment in prehistoric rock art around the world.…”