Pyrite-uranium polycrystal

A texture was observed in a sample of ore in 'Which pyrite and uraninite occurred as thin alternate layers paralleling crystal faces of a pyrite nucleus. This texture could be formed either by replacement or by syntaxis. Although syntactic growth forming polyerystals of two chemically dissimilar minerals has not been previously described, this explanation fits the observed data better than the explanation offered by replacement. It is proposed, therefore, that this occurrence is an example of a polycrystal of uraninite and pyrite and that the mechanism of formation is syntaxis.