Lunar samples volcanic glasses

Mare basalts include lavas that erupted from fissures and pyroclastic deposits that produced glass beads. Six of the nine missions to the Moon that returned samples included basalts. The mare basalts from different sites have distinctive compositions and are classified based on their Ti02 contents, and to a lesser extent on their potassium contents (Fig. 13.3). A further subdivision is sometimes made, based on A1203 contents. Mare basalts are compositionally more diverse than their terrestrial counterparts. Volcanic glass beads, formed by fire fountains of hot lava erupting into the lunar vacuum, were found at several Apollo sites and eventually were shown to be a constituent of virtually every lunar soil. The glasses are ultramafic in composition and formed at very high temperatures. 

Figure 4 Plotted on a log scale, and with fundamentally related (artificially oversampled) suites averaged together (as in Table 2), mare volcanic samples exhibit a possible bimodality in Ti02 content, but with the gap in the distribution at around 1-2 wt.%, not 6-9 wt.% as commonly claimed (see text). Lunar meteoritic data, including pyroclastic glass suites (Arai and Warren, 1999), are distinguished by longer symbols.

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