1. A method of analyzing an earth formation, the method comprising: a) conveying a tool in a borehole in the earth formation; b) pulsing the formation with radiation from the tool; c) detecting gamma rays resulting from interaction of the pulsed radiation with a plurality of elements in the formation, the plurality of elements including Aluminum (Al); and (d) estimating from a determined spectrum of the gamma rays an elemental concentration of Al and at least one additional element.