Digital ACT Science Practice Question #1813

Which of the four tested mineral specimens is capable of scratching all of the other three? Experiment Context (Physical Identification of Geological Minerals): Geology students performed diagnostic physical property tests on four unknown mineral samples (W, X, Y, Z): Table 20: - Mineral W: Mohs Hardness = 2.5 (scratched by copper penny); Streak = White; Reaction to cold 10% HCl = No reaction - Mineral X: Mohs Hardness = 3.0 (scratches copper penny); Streak = White; Reaction to cold 10% HCl = Vigorous effervescence (bubbling) - Mineral Y: Mohs Hardness = 5.5 (scratches glass plate); Streak = Reddish-brown; Reaction to cold 10% HCl = No reaction - Mineral Z: Mohs Hardness = 7.0 (scratches steel file & quartz); Streak = White/None; Reaction to cold 10% HCl = No reaction