THERE has been great controversy as to whether or not there exist in Brazil diamond-bearing “pipes” such as are found in South Africa. That something of the kind should exist seems to be pretty well acknowledged, but any evidence in support of the discovery of a “pipe” has always been very meagre. The following observations made by the writer on a few mines in the neighbourhood of Diamantina, in the state of Minas Geraes, might be of interest on this somewhat vexed question.