Algal structures with a variety of forms are recognized in the ore-bearing Precambrian rocks of the Mufulira mine area. Algal reefs occur at the margin of the B ore body, in the underlying dolomite. Dolomitic mottling in quartzite is continuous with underlying stromatolites and is interpreted as algal in origin. On a small scale, copper is more abundant in clastic material in the interstices of algal structures than in the algal dolomite. The B ore body ends where the underlying bed becomes strongly dolomitic. This antipathetic relation of copper and carbonate is believed to favor a syngenetic origin for the copper.