Figure 5.04. Fe-rich rim on olivine. Crossed polarized light image of olivine phenocryst in basalt from Mauna Loa Volcano, Hawaii. The second-order blue retardation of the rim on the first-order red olivine crystal is due to the increased iron content of the rim. The crystal is 0.8 mm long and is surrounded by a glassy groundmass containing plagioclase laths.
