The invention provides a method of assaying a mineral sample for determining the concentration of selected metals in a sample comprising the steps of providing a comminuted mineral sample; mixing such sample with a flux; preheating a reaction vessel to a temperature which approximates the melting point of the flux; introducing the mixture of the mineral sample and flux into the crucible, whereby the mixture is transformed to a molten state to capture the metal to be assayed in a collector material; and separating slag from the collector material.