Pseudotectites from Colombia and Peru

In a previous note on “Americanites” (Martin, 1934) from Colombia and Peru, the writer came to the conclusion, on the basis solely of published data, that it was very likely that these so-called tectites are in reality obsidian of terrestrial origin. He stated, however, that “before it is possible to separate the americanites definitely from the tectites, a detailed field examination is required and also a minute determination of the chemical composition of the americanites and of the indubitable volcanic rocks from the neighbourhood.” A generous contribution from the Molengraaff-Fonds enabled the writer in the summer of 1934 to make a special study of tectites, in the course of which he visited the Mineralogical Institute at Jena, (Germany, where he had occasion to study the Paucartambo (Peru) “tectite” and a few of the “tectites” from Colombia. This short investigation showed already that the flat-bottommed surface observed on the ""tectite"" from Paucartambo and on some obsidian spheres from Cali (Colombia) is not a part of the original surface of the “teetite” body but a subsequently developed fracture surface of slightly conchoidal shape, and should consequently not be explained as a flattening of the “tectite” due to falling from the heavens in a semi-plastic condition. The long paragraph dedicated to the explanation of this phenomenon in the former publication (p. 129) can therefore be stricken from the evidence presented in connection with the problem of the origin of these bodies.