- megacycle
- meionite
- Meishucun Formation
- Meishucunian Age
- Meishucunian Stage
- Meitan Formation
- melange
- melanocrate
- melilite
- meliphanite
- melting curve
- member
- Menevian Age
- Menevian Stage
- Menkadun Formation
- meridional structural system
- meridional tectonic belt
- mesocratic rock
- mesodesmic structure
- Mesoproterozoic Era
- Mesoproterozoic Erathem
- mesosiderite, pyroxene-plagioclase stony-iron
- mesothermal deposit
- Mesozoic Era
- Mesozoic Erathem
- mesozone
- Messinian Age
- Messinian Stage
- meta-gabbro
- metabasite
- metal nickel-iron
- metallic luster
- metallic mineral
- metallo-organic complex
- metallo-organic matter mineralization
- metallogenesis, minerogenesis
- metallogenic belt
- metallogenic domain, metallogenic megaprovince
- metallogenic epoch
- metallogenic prediction
- metallogenic province
- metallogenic region
- metallogeny
- metamict
- metamorphic cycle
- metamorphic differentiation
- metamorphic episode
- metamorphic epoch
- metamorphic event
- metamorphic facies