With initial reference now to FIG. 1, a furnace constructed in accordance with the teachings with the present invention is generally indicated by the reference numeral 10. Furnace 10 is operationally illustrated coupled to a conventional, spaced-apart cyclone separator 12. Expandable raw ore such as vermiculite or perlite will be delivered through conventional conveying techniques into a conduit 14 for subsequent injection interiorly of the furnace 10. Minerals expanded within the furnace will rise upwardly, being outputted through a shroud 16 and duts 18, 20 for tangential input at the top of cyclone separator 12. Hot expanded ore product delivered into the separator will fall downwardly through lower frusto-conical portion 24 for delivery to a suitable container or conveying apparatus via output tube 26 and orifice 27. Waste gases are conventionally outputted through an upper exhaust 28.