Guariba

This irregularly shaped intrusion, approximately 5x2.5 km, consists principally of syenites but with granites and trachytes/phonolites also occurring. The syenites comprise essentially perthite, a little oligoclase, rare quartz, biotite, plentiful hastingsite and rarer riebeckite or arfvedsonite. The granites are apparently not peralkaline, but the trachytes, which form dykes and included blocks, contain phenocrysts of K-feldspar, abundant aegirine and cancrinite, which is considered to be primary, while fine micaceous patches are thought to be after nepheline. Rare violet fluorite occurs and carbonate is also present.