To determine the role of mineralogy and composition on the microbial ecology of the deep igneous marine biosphere, we incubated twelve igneous minerals and glasses in IODP Hole 1301A on the eastern flank of the Juan de Fuca Ridge (47° 45.210' N, 127° 45.833' W) for four years (2004 – 2008) (Smith et al., 2011). Hole 1301A is a subseafloor microbial observatory equipped with a Circulation Obviation Retrofit Kit (CORK) that allowed us to suspend microbial flow cells 262 m within the basalt basement, exposing common igneous minerals and glasses to the aquifer community. Pyrotag sequencing revealed that the mineral olivine was dominated by the uncultured, and thus uncharacterized, archaeum Archaeoglobaceae OTU 5. The low complexity of the microbial community associated with olivine makes this an ideal candidate for shotgun metagenomic sequencing, with the explicit goal of reconstructing the metagenomes of members of the Archaeoglobaceae. Given that olivine is one of the most abundant minerals in oceanic crust, understanding the functional role of the uncultured Archaeoglobaceae in biogeochemical cycling in the marine subsurface is imperative and has the potential to provide transformative knowledge regarding mineral weathering on a global scale. We predict that Archaeoglobaceae OTU 5 is using either an iron-based or hydrogen-based metabolism on olivine surfaces, and it may be a major primary producer in olivine-rich crust.