An igneous or metamorphic rock composed chiefly of one or more ferromagnesian, dark-colored minerals; also, said of those minerals.
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Glossary
Mafic
Marble
A metamorphic rock consisting predominantly of fine- to coarse-grained recrystallized calcite and/or dolomite.
Metaigneous Rock
A metamorphosed igneous rock.
Metamorphic Rock
A rock derived from metamorphism of a pre-existing rock.
Metamorphism
Recrystallization of solid rock at variable temperatures and/or pressures below the Earth’s surface, producing changes in the rock’s texture or composition.
Metasedimentary Rock
A metamorphosed sedimentary rock.
Mica
A group of hydrous aluminum-rich silicate minerals, all of which have perfect basal cleavage that allows them to be peeled apart in thin layers (e.g., muscovite, biotite).
Mineral
A naturally occurring, inorganic substance having an orderly internal crystalline structure, characteristic chemical composition, and physical properties.
Modified Slope
A slope that has been significantly altered by humans by construction activities (such as roads, cuts, fills, etc.).
Mud
A mixture of fine silt- and clay-sized particles.
Muscovite
A transparent to silvery-colored potassium-bearing mineral of the mica group.
Mylonite
Any foliated and usually lineated, fine-grained metamorphic rock which shows evidence of strong ductile deformation related to movements along a ductile fault zone.