1. Hard as granite
   - granitic, rocklike, stony

See also: hard

• family Moniliaceae
• family Monocanthidae
• family Monodontidae
• family Monotropaceae
• family Moraceae
• family Morchellaceae
• family Motacillidae
• family Mucoraceae
• family Mugilidae
• family Mullidae
• family Muraenidae
• family Muridae
• family Musaceae
• family Muscicapidae
• family Muscidae
• family Musophagidae
• family Mustelidae
• family Mutillidae
• family Myacidae
• family Mycetophylidae
• family Mycobacteriaceae
• family Mycoplasmataceae
• family Myctophidae
• family Myliobatidae
• family Mylodontidae