Fig. 1.  Atomic Si-Mg-Fe ternary diagram shows the range of compositions for three types of glasses observed in ALH 84001. In general, the pyroxene-like composition glasses are enriched in Al compared to clinopyroxene and orthopyroxene. The Si-rich glasses include minor amounts of Fe (<0.5 wt%), Mg (<2.2 wt%), and Ca (<3.2 wt%).