1. a single chemical compound or element that is found in nature amorphous 2. the amount of kinetic energy that a material can absorb without breaking cleavage 3. a break that does not follow a flat surface, but rather is rough and uneven crystal 4. resistance to being scratched fracture 5. a solid form resulting from the arrangement of atoms, ions, or molecules in definite geometric patterns hardness 6. a clean break parallel to planes of weakness in a crystal mineral 7. a non-crystalline solid having no orderly arrangement of molecules toughness