Eight pyroxenes from the ultramafic peridotite of the Dawros promontory on the western coast of Ireland have been analyzed. The chemical data are given here, together with a rock analysis. Three are primary pyroxenes from the layered peridotite resulting from fractional crystallization, four are recrystallized pyroxenes from deformed peridotite, and one is possibly a metamorphic pyroxene. It is associated with green spinel and ore, and shows a high Al 2 O 3 content. The pyroxenes are compared with those from other areas, and the indications of recrystallization and metamorphism which make comparison difficult are discussed.

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