Fungal attack on rock: solubilization and altered infrared spectra.

Penicillium simplicissimum, isolated from weathering basalt, produced citric acid when grown in a glucose-mineral salts medium with basalt, granite, granodiorite, rhyolite, andesite, peridotite, dunite, or quartzite. After 7 days' growth as much as 31 percent of the silicon, 11 percent of the aluminum, 64 percent of the iron, and 59 percent of the magnesium in some of the rocks were solubilized, and a number of rocks showed altered infrared absorption in the silicon-oxygen vibration region.