How do geologists classify metamorphic rocks? ... Extreme pressure squeezes rock so tightly that the mineral grains may line up in flat, parallel layers. Geologists classify metamorphic rocks. according to the arrangement of the grains that make up the rocks.

Do Geologists classify rocks?

Geologists classify rocks in three groups, according to the major Earth processes that formed them. The three rock groups are igneous, sedimentary, and metamorphic rocks. Anyone who wishes to collect rocks should become familiar with the characteristics of these three rock groups.

What are the classifications of metamorphic rocks?

Metamorphic rocks are broadly classified as foliated or non-foliated. Non-foliated metamorphic rocks do not have aligned mineral crystals. Non-foliated rocks form when pressure is uniform, or near the surface where pressure is very low.