Lunar meteorite ALHA81005 contains a clast of ferroan anorthositic troctolite with (in vol %) 59% plagioclase (avg. An 95.4), 27% olivine (avg. Fo 52.2), 11% clinopyroxene (mg 50--70, Wo 11--34), and 3% chlorapatite. This clast is probabily pristine and is unique among lunar samples. Its texture is igneous, but is unusual in that pyroxene and apatite, which probably cocrystallized, have been brecciated and apparently resorbed, and olivine has precipitated around them. We discuss four possible explanations for this texture: (1) a sudden decrease in pressure occurred, causing liquidus pyroxene to become unstable relative to olivine; (2) the bulk composition of the magma was sufficiently FeO-rich that pyroxene crystallized before olivine; (3) a P2O5-rich (2.5--3.0 wt %), quartz-normative, basaltic magma that crystallized pyroxene, plagioclase, and phosphates was mixed with an olivine-saturated magma that had a lower P2O5 content; (4) an olivine-saturated magma invaded a wall rock assemblage of pyroxene, plagioclase, and apatite. The first two models require only one magma and are attractive because the average compositions of pyroxene, olivine, and plagioclase indicate that they crystallized from liquids with similar mg. The first model cannot be assessed without knowing the bulk composition of the original magma and the initial pressure. The second model cannot account for the brecciation and resorption of the pyroxene and apatite. A model involving either magma-mixing or wall rock-magma reaction seems most likely. The high P content and apatite/whitlockite ratio indicate that the parent magma(s) had an unusually high volatile content for a lunar magma. REE in whitlockite are 40--80 times KREEP abundances. The parent magma(s) must have had very high abundances of REE and La/Sm less than that of KREEP. The clast is also unusually mafic (only 59% plagioclase) for pristine ferroan rocks. Ferroan mafic lithologies appear to be an important component of ALHA81005. The apatite-rich clast presents several petrologic and geochemical paradoxes, which suggests that complex processes were involved in its formation.