The Origin of Diamonds in Drift of the North Central United States: A Discussion

H P. Schwarcz's hypothesis (Schwarcz, 1965) on the possible meteorite crater in Hudson Bay is plausible, but his conclusion that there is a relationship with the diamonds in the drift of the northern United States is too tenous to pass without comment. Dr. Schwarcz himself states (Schwarcz, 1965, p. 662) that he could not find any coesite, a high-pressure polymorph of silica, in a till sample to the south of Hudson Bay.3 Further, he concedes that the presence of a meteorite crater is no more than inferred from an unusually shaped and discordant coast line and from association with other supposed meteorite craters (Schwarcz, 1965, p. 659). No direct field evidence has yet come to light. I do not wish to dispute the existence of a meteorite crater, even though such a conclusion may be premature. However, the possibility that such an impact caused diamantiferous eruptions which have been fortuitously elevated but preserved from erosion until the Pleistocene is very remote and even more speculative. In the light of evidence for a more normal origin for the diamonds, such a hypothesis should be regarded with caution. It is by no means clear from which direction (or directions) or how far the drift diamonds have come. The transport pattern used by Schwarcz (1965, p. 660) is simplified and is essentially that drawn by Hobbs (1899)4 based on late Wisconsin endmoraine patterns, erratics, eskers, drumlins,