meet at an angle of 90° or near 90° 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 Quartz White Curved conchoidal 7 fracture; occurs as crystalline quartz and as bluish _chalcedony_ D. Cannot be scratched by quartz Topaz White Perfect basal 8 cleavage gives flat, plate-like fragments; notice hardness 13. NONMETALLIC luster, RED or PINK color