Sagvandite forming a coarse-grained veinlike zone in one of three ultrabasic intrusions recognized on the island of Berneray in the Outer Hebrides (Scotland) is essentially a dolomite-orthopyroxene rock containing some olivine. Limestone assimilation is ruled out as an explanation of the origin of the sagvandite. Metasomatic processes accompanying the introduction of CO 2 along a fissure are suggested as more consistent with the composition and mode of occurrence. The age and source of the introduced material are not known.