Why large crystals are often brown?explain.?
If large crystals are brown it is likely that small crystals of the same substance are also brown. You see brown when the correct mix of photons are received in the eye and perceived by the three types on color-sensing cones. For a small crystal the same mix of colors are sent but not enough photons may be available to identify the color, except perhaps under a microscope that would concentrate the photons onto a larger area of the retina. Of course crystals may have their own color or may reflect or transmit any external colored light. Crystals may also transmit or reflect light differently depending upon how the crystal lattice is oriented with respect to the eye and may have a prism effect depending upon the shape.
