Altered basic to intermediate composition fine-grained igneous rock in which the feldspar
is partially or completely composed of of albite, typically accompanied by chlorite,
calcite, quartz, epidote, prehnite, and low-tempaerature hydrous crystallization products.
Preservation of eruptive volcanic features is typical.
Fettes and Desmon, 2007; Best, M.G., 1982, Igneous and metamorphic petrology: New
York, W.H. Freeman and company, p. 398; Neuendorf et al. 2005, p. 619.