HYDROTHERMAL ALTERATION OF KIMBERLITE IN ACID MEDIA WITH ALUMINIUM ION ADDITIONS.

The physico-chemical processes resulting in the breakdown of kimberlites were studied as an alternative to comminution as a means of liberating diamonds. A sample of Wesselton kimberlite (48 wt% serpentine, 35 wt% olivine and 10 wt% calcite) was treated with mineral acids and salts at 343K and 373K. Reactions in the presence of sulphuric acid resulted in simple fragmentation of the feed. Reactions in hydrochloric and nitric acid media induced alteration to vermiculite; more complex assemblages were produced on addition of the Al**3** plus ion, with chlorite, saponite, kaolinite and septechlorite being detected. The addition of Al**3** plus increased the extent of physical degradation due to acid regeneration. Diagrams relate the phases formed to the experimental conditions used.