A. Cannot be scratched by a copper penny but can be scratched by an ordinary pocket knife Fluorite White Cleavage in 4 4 directions can give fragments that are shaped like octahedrons; crystals commonly cubes B. Cannot be scratched by an ordinary pocket knife but can be scratched by quartz Quartz, variety: White Curved, 7 amethyst conchoidal fracture; _amethyst_ crystals commonly 6-sided prisms with pyramid-like ends 15. NONMETALLIC luster, COLORLESS A. Can be scratched by a fingernail Cerargyrite Shiny white or Appears waxy; 1-1½ gray knife cuts it smoothly; turns violet brown to black when exposed to light Gypsum White Transparent 2 selenite variety commonly occurs as flat, diamond-shaped crystals; splits into thin, flat sheets that will not bend without breaking Muscovite (white White Splits into thin, 2-2½ mica) flat, transparent sheets that will bend without breaking B. Cannot be scratched by a fingernail but can be scratched by a copper penny Barite White Rather heavy; 3-3½ cleavage