Video Transcript
When identifying a mineral, why is
it more reliable to use a mineral’s streak over a mineral’s color? (A) A mineral’s streak is always
the same, whereas a mineral’s color can change due to impurities. (B) A mineral’s streak can change
due to minute gas bubbles, whereas a mineral’s color is always the same. (C) A mineral’s streak can also
tell you about the mineral’s light-reflecting tendencies, whereas a mineral’s color
cannot. (D) A mineral’s color is always the
same, whereas not all minerals have a streak.
The color of a mineral depends on
its composition. Some minerals display more than one
color. This happens when the crystal
structure contains impurities or imperfections. For example, the mineral fluorite
may be colorless, purple, blue, green, orange, pink, or yellow. As some minerals have a variety of
colors, mineral color is not a diagnostic property. This means that it cannot be relied
on to identify a mineral.
Mineral streak is a much more
reliable way to determine the identity of a mineral. Mineral streak is the color of a
mineral in its powdered form. It can be obtained by rubbing the
mineral on a hard, white surface, such as a tile of unglazed porcelain or streak
plate. The streak test is important
because many minerals display a variety of colors. But all specimens of that mineral
will display the same streak color. For example, while fluorite can
occur in a variety of colors, its streak is always white.
Therefore, when identifying a
mineral, it’s more reliable to use a mineral’s streak over a mineral’s color because
the mineral’s streak is always the same, whereas the mineral’s color can change due
to impurities.
