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). Clinopyroxene and plagioclase compositions in both gabbro types (Fs7--14Wo41--47; Al2O3 3--4%) (An52--89Or0.5--3) indicate that these xenoliths are products of Hawaiian magmatism and not N-type mid-ocean ridge basalts. These phases plus olivine compositions (Fo71--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 xenolths) 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. ¿ American Geophysical Union 1988