It is understood and agreed that this lease covers and includes oil and gas only (including with oil and gas, all constituent elements thereof and all other liquid or liquefiable hydrocarbons and products of every kind or character derived therefrom and produced therewith, including sulphur), and that all minerals other than oil and gas are excepted herefrom and reserved to Lessor. Included among the minerals reserved to Lessor and excluded from this lease are coal, uranium and lignite.