Abstract
There has been much controversy over the importance of sulphide-silicate liquid immiscibility in the genesis of the nickel deposits that are associated with basic rocks. Except that the position of the ores in the igneous bodies supports the idea of gravitative settling of fluid sulphides, little field evidence in favor of the theory has been noted. Some observers require as proof the occurrence of globules of one component suspended in a matrix of the other. Grout mentions that during slow crystallization, the globules might lose their rounded form, and believes that the sulphides at Sudbury have passed through this stage. In material from the Gap Nickel Mine in Pennsylvania, the writer believes that evidence of sulphide-silicate unmixing is offered by rounded masses of amphibole occurring in the sulphide matrix.
