A low-grade metamorphic rock, slate is derived from pelitic rocks. Green slate is formed from quartz, some feldspar, and mica. The presence of chlorite gives this slate its green color.

TEXTURE Fine-grained, with grains of a similar size. The grain size is too fine to be seen without a microscope.

ORIGIN Forms when fine-grained sediments, such as clay or volcanic ash, undergo regional metamorphism. Minerals like mica and chlorite become aligned, giving a perfect, slaty cleavage.

Group: METAMORPHIC

Grain size: Fine

Classification: Regional

Pressure: Low

Temperature: Low

Structure: Foliated