A minor phase in iron-ore sinters has been synthesized and identified as a clinopyroxene with the approximate formula Ca1·0(Ca0·14Fe0·863+)(Fe0·323+Al0·60Si1·08)O6. This composition shows that it consists largely of the hypothetical Tschermak's molecule, M2+R23+SiO6. The small size and sparse distribution of this phase in most iron-ore sinters has previously hindered analysis.