FOURIER-TRANSFORM RAMAN-SPECTROSCOPIC STUDY OF PIGMENTS IN NATIVE-AMERICAN INDIAN ROCK ART - SEMINOLE CANYON

Samples of rock art (ca. 3000-4200 years BP) from the Lower Pecos regi on of Texas, near the confluences of the Pecos and Devils rivers with the Rio Grande, have been analysed using Raman microscopy. This rock a rt represents some of the finest pictographs known in North America. T he red pigment is confirmed to be red ochre (iron (III) oxide and clay ) whereas the black pigment is manganese (IV) oxide. White areas of th e paintings are identified as calcium oxalate monohydrate (whewellite) , whose presence could indicate the previous colonisation of the shelt er walls by lichens. The black pigmented areas only contained Raman sp ectroscopic evidence for organic matter which was probably used as a b inding agent. (C) 1998 Elsevier Science B.V. All rights reserved.