In an article by Mr. Th. Gathmann, • on the so-called "itabirite" iron ores of Minas Geraes, Brazil, in/he May number of the Zeitschrift fiir Praktische Geologie the writer cites evidence for, and attempts to prove, that these ores are secondary surface deposits formed by the leaching of silica from an iron-oxide bearing quartzite for which the term itabirite has been adopted. Mr.. Gathmann admits that he has seen only a very small part'of the district, in fact that his observations have been

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... mited to an area a few kilometers square in a district which is several hundred kilometers in extent, and it happens, unfortunately, that this area is rather more complex geologically than most of the rest of the district, making it difficult to see the relation of the differ• ent fomations to each other. As a result of three years spent in exploration work, both surface and underground, in various parts of the Minas Geraes iron ore field, I have.gained a different impression of the nature of the "itabirite ores" from that held by Mr. Gathmann; so that it seems well to record my observations and state deductions which I have drawn from them. x Gathmann, Th., "Beltrag zur Kenntnis der 'Itabirit' Eisenerze in Minas Geraes (Brasilien)," Zeitschrift fiir Praktische Geologie, XXI. Jahrg., Mai, I913, s. 234 his 240. IOI