Andesite Lava

The black crystals in this specimen are the water-bearing minerals amphibole and biotite: evidence of the magma's high water content. The abundant large white crystals of plagioclase helped make the magma highly viscous.

Group: Igneous
Catalog Number: 116619.0048
Time Period: Erupted 1.7 million years ago
Locality: Sutter Buttes , California