Feldspar White Glassy or pearly 6 luster; good cleavage in 2 directions that meet at an angle of 90° or near 90°; common in granite and pegmatite rocks Opal White Curved, 5-6 conchoidal fracture; may appear glassy, greasy, resinous, or dull Quartz White Curved conchoidal 7 fracture; occurs as chert and chalcedony 8. NONMETALLIC luster, YELLOW color A. Can be scratched by a fingernail Carnotite Yellow Bright canary 2 yellow or lemon yellow; radioactive; occurs as crusts and powdery masses Gypsum White Yellowish; soft; 2 occurs as crystals or as fibrous, granular, compact or earthy masses Limonite Rusty yellowish Brownish-yellow 1+ brown color; may be soft and earthy Muscovite (white White Light colored; 2-2½ mica) splits into thin, flat, transparent sheets that will bend without breaking Sulfur White or pale Will burn with a 1½-2½ yellow blue flame;