Final answer:
The rock's property that is determined by its color is simply known as Color (D). Color can be influenced by various factors including mineral content and impurities but may be non-diagnostic because it can change due to environmental influences.
Step-by-step explanation:
The student asked, "Fran finds a dark color rock that she identifies as basalt. Which property gets the rocks by color?" The answer is D) Color.
The color of a rock or mineral is a direct observation of its appearance and is one of the most obvious physical properties. It varies based on the rock's or mineral's chemical and mineral composition. It is essential to note that color is often non-diagnostic for identifying minerals because different environmental factors can alter it; therefore, other properties such as hardness, streak, and luster are also used in identification processes.
Hardness is a measure of how easily a mineral can be scratched and is gauged on the Mohs scale. Streak is the color of the mineral in its powdered form, which may or may not correspond to the color of the larger mineral sample. Luster refers to how light is reflected from a mineral's surface and can be either metallic or non-metallic.
In color identification, impurities often play a role, although they can sometimes mislead the observer. In the case of basalt, a dark coloration is typical due to its mineral content, which often includes minerals like pyroxene and olivine that absorb more light, giving the rock a darker appearance.