A process for obtaining one or more metal fluoride or metal oxide compounds from treatment of a feed material containing aluminium ore, includes the steps of contacting the feed material with a fluorine acid solution to form gaseous silicon fluoride and aqueous soluble metal fluorides and/or metal fluosilicates, processing the aqueous reaction products to form a solid reaction product containing metal fluorides, processing to remove low boiling point compounds and heating said solid reaction product to a temperature to drive off metal fluoride in gaseous form. The feed material may include aluminium ores and/or titanium ores, coal or other carbonaceous materials containing mineral impurities, or other minerals such as mica. Processes for the production of aluminium and titanium compounds are also described.