Which properties are most useful for identifying minerals? why?

Which of these properties, used alone, would be least useful in identifying most minerals? a. color b. luster c. streak d. density

Why are people not able to scuba dive in the deep part of the ocean

Three cards with holes are arranged in a straight line. a light is shined through the first card’s hole and travels through all three cards. what does this tell you about light rays? a) that light is reflected b) that light is refractive c) that light travels in a straight line d) that light does not travel in a straight line