Gabbroic xenoliths from the hawaiite summit cone of Mauna Kea volcano, Hawaii, are up to 15 cm in size and form two groups: olivine (+pl+cpx) gabbros and opaque-oxide (+pl+cpx) gabbros. Both types have members that are laminated and probably cumulate in origin, and each type has interstitial glass of hawaiitic-mugearitic composition. Olivine gabbros have MgO 12–25 wt.%, FeO^* 4–12%, and TiO₂ 0.5–1%, whereas opaque-oxide gabbros have MgO about 6 wt.%, FeO^* 12–18%, and TiO₂ 5–7% (due to 11–27 vol.% Fe-Ti oxides). Cli-nopyroxene and plagioclase compositions in both gabbro types (Fs_7–14 Wo_41–47; Al₂O₃ 3–4%) (An_52–89 Or_0.5–3) indicate that these xenoliths are products of Hawaiian magmatism and not N-type mid-ocean ridge basalts. These phases plus olivine compositions (Fo_71–84), paragenesis, and mixing models using representative Mauna Kea basaltic rocks indicate that the gabbros are crystalline products from mafic alkalic parent basalt (e.g., ∼8 wt.% MgO). Modeling shows that residual liquid after 25–30% crystallization of ol+pl+cpx (the xenoliths) may be basalt/hawaiite of the Hamakua Volcanics on Mauna Kea. Alternatively, 60% crystallization of ol+pl+ cpx+mt+il feasibly produced liquid represented by the hawaiite of Laupahoehoe Volcanics; interstitial glass may represent liquid after more than 60% crystallization. Crystallization depth was shallow if daughter magmas were Hamakua, but was at least at 8-kbar pressure if Laupahoehoe hawaiites were produced (due to absence of liquidus cpx in Laupahoehoe rocks). Laupahoehoe hawaiite transported the xenoliths to the surface.