Minerals first identified in Apollo 11 samples
Three minerals new to science were first described from the Apollo 11 rocks — the Moon is their type locality. Each reflects the distinctive chemistry of the high-titanium mare basalts: iron- and titanium-rich, water-free, and crystallized under very low oxygen.
- Armalcolite — an opaque (Mg,Fe²⁺)Ti₂O₅ titanium oxide, named for ARMstrong, ALdrin, and COllins. It crystallizes early and is commonly mantled by ilmenite; the Compendium records “magnesian armalcolite with ilmenite overgrowth” in 10072, and it appears across the high-Ti basalts (9 of the sampled rocks).
- Tranquillityite — a late-stage Fe,Ti,Zr-silicate, named for Tranquility Base. Lovering et al. (1971) “defined it as tranquillityite” from sample 10047, where it occurs as rare rods in the residual melt.
- Pyroxferroite — an iron-rich pyroxenoid, (Fe,Ca)SiO₃, forming the Fe-rich rims of strongly zoned pyroxenes as the last melt crystallized; described by Frondel et al. (1970) and Chao et al. (1970) from 10047.
Armalcolite marks the early high-Ti crystallization, while tranquillityite and pyroxferroite are late, concentrated in the iron- and incompatible-element-rich residual liquid — together they trace a basalt’s crystallization from first to last. All three were later found in other lunar samples (and armalcolite and pyroxferroite in some meteorites and terrestrial rocks), but Apollo 11 is where they were first recognized. These identifications are documented through the per-sample Lunar Sample Compendium entries, which also catalogue the more common phases — pyroxene, plagioclase, ilmenite, cristobalite, troilite, and native iron — of the type A and B rocks.