Optimal compositions of the borax bead for analysis of silicates, as glazes, mosaics, mor-tar, stone, glass, and ceramics, at the Research Laboratory of the Museum of France are determined. The borax bead and sample are fused, and then examined by x-ray diffraction. Borax beads are optimally prepared with a flux of Li tetraborate and La₂O (type B 106) at dilu-tions lte 20. -- AATA