Of the metals in the series Sc, V, Cr, Mn, Fe, and Ga pyroxenes of the type LiM³⁺Si₂O₆ were obtained only from Sc, V, Cr, and Fe in dry synthesis experiments near 1000 °C. Ga and A1 gave keatite derivatives (so-called ‘β-spodumenes’) by dry heating; α-Ga-eucryptite was obtained from Ga hydrothermally at pressures between 4·5 and 6·5 kb. Mn gave Mn₂O₃. The lattice parameters of the pyroxenes vary irregularly with atomic number. This variation and the failure to produce a Mn³⁺-pyroxene can be explained by the crystal-field theory. At high temperatures A1 and Ga are too small to stabilize a silicate pyroxene phase even at moderately high pressures and form less dense tectosilicates. The octahedral stabilization energy for Cr³⁺ ensures that Cr, which has the same size as Ga, forms a pyroxene.