Values for the Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Nb, Sn, Ba, La, and Pb contents of the new U.S.G.S. silicate rock standards are given. The results were obtained by X-ray fluorescence analysis. A calibration method was used which involved spiking of the samples with small quantities of the elements to be measured. This avoided the errors due to matrix effects, usually associated with the analytical technique. © 1969.