MCP experiments were conducted in Retsch PM-100 planetary ball mill. The prepared reactant mixtures with 10–40 wt.% excess amounts of both Mg and B2O3 were placed in a gas tight, 250 ml volume stainless steel grinding jar together with 8 pieces of 20 mm diameter stainless steel grinding balls. Ball to powder weight ratio was taken as 1/15 and grinding jar was evacuated, flushed and then filled with argon gas before the experiments. The planetary ball mill was operated for 30 or 40 h at 300 rpm.