as sugary-looking masses Azurite Blue Bright, intense 3½-4 blue color; dilute hydrochloric acid will fizz on azurite Barite White Rather heavy; 3-3½ cleavage fragments may be flat and slab-like Celestite White Not quite as 3-3½ heavy as barite; crystals commonly prism-shaped or flat-looking; some cleavage fragments are flat and slab-like Fluorite White Cleavage in 4 4 directions can give fragments that are shaped like octahedrons; crystals commonly cube-shaped Opal White Curved, 5-6 conchoidal fracture; may appear glassy, greasy, resinous, or dull; milky white and bluish-white precious opal shows plays of colors C. Cannot be scratched by an ordinary pocket knife but can be scratched by quartz Feldspar White Glassy or pearly 6 luster; good cleavage in 2 directions that