fragments Celestite White Crystals commonly 3-3½ prism-shaped or flat-looking; some cleavage fragments are flat and slab-like Halite White Salty taste; 2½ dissolves in water; cube-shaped cleavage fragments Sulfur White or pale Will burn with a 1½-2½ yellow blue flame; commonly found as crystals, crusts, or grains C. Cannot be scratched by a copper penny but can be scratched by an ordinary pocket knife Anhydrite White Commonly occurs 3-3½ as sugary-looking masses Celestite White Crystals commonly 3-3½ prism-shaped or flat-looking; some cleavage fragments are flat and slab-like Dolomite White Commonly occurs 3½-4 as granular masses and as rhomb-shaped crystals; dilute hydrochloric acid may fizz slightly on dolomite Opal White Curved, 5-6 conchoidal fracture; may appear glassy, greasy, resinous, or dull D. Cannot be scratched by an ordinary pocket knife but can be scratched by quartz