We developed a fusion glass disc technique using small-size samples (30 mg) for assaying precious siliceous samples of geochemical reference materials using wavelength-dispersive X-ray fluorescence determination of major (SiO 2 , TiO 2 , Al 2 O 3 , TFe 2 O 3 , MnO, MgO, CaO, Na 2 O, K 2 O, and P 2 O 5 ) and minor (Ni, Sr, and Zr) elements. The normal-size glass discs (approximately 30 mm in diameter) were prepared using an automatic fluxer, combined with manual preparation, with a flux to sample ratio of 100 : 1. GSR-1 and GSR-3 were selected to evaluate the results obtained using XRF, ICP-OES (fusion), and ICP-OES (acid attack) and to assess the accuracy and precision of the three methods based on Whitty-Léveillé and coworkers' protocol. In the present work, a set of 46 rock certified reference materials (CRMs) was used to calibrate the spectrometer and another set of 16 CRMs was analyzed further to validate the accuracy and precision of the procedure. The homogeneity of the discs was evaluated using the μ-XRF mapping image technique. In general, we obtained good agreement with the recommended values for most determinations. Finally, we summarized the small-size sample methods published in recent years and compared the advantages and disadvantages of these methods in detail. This paper proposed a semi-automated small sample (30 mg) preparation method. The accuracy and precision of this new method were verified by measuring two CRMs among XRF, ICP-OES (fusion), and ICP-OES (acid attack) tools.