Crystal Colors
Published On: 11-22-2011 06:05pm
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Category: Crystals
Crystals may be found in all the colors of the rainbow. Some minerals are opaque and always hold just one color, while the majority of crystals come in a variety of colors due to minute impurities.
Crystals that contain light absorbing atoms as an intrinsic part of their chemical structure are just one color. For example, malachite is always green, lapis lazuli always blue. These gems have a stable crystal structure that cannot be altered by heat or irradiation.
The majority of crystals, however, contain small imperfections and impurities within their chemical structures. Their colors then originate from these trace atoms that distort the crystal lattice and deflect or alter light rays as they pass through. For example, transparent quartz can appear violet when iron atoms are present, pink with titanium or manganese, and even smoky brown when subjected to natural radiation from uranium, intense gamma rays from space, or ultraviolet radiation from the sun. The beryl family includes green emeralds (chromium), yellow heliodor (iron), and pale rose to violet morganite (manganese). Green tourmaline (see our last issue on all tourmaline varieties) derives its color from sodium.
Many gemstones can be heat-treated or irradiated to enhance or change their color. The carefully heating of aquamarine will deepen its natural sea-green hue to sky or dark blue. Heated amethyst will turn yellow and resemble citrine. In fact, since this mineral is relatively rare, most citrine on the market today is heated amethyst.
Internal fractures and dislocations within a crystal lattice will also create beautiful plays of color and light so that a variety of color effects may be seen within a single crystal depending on the angle at which it is viewed. Examples may be found within tourmaline, aquamarine, morganite and labradorite.
Crystals that contain light absorbing atoms as an intrinsic part of their chemical structure are just one color. For example, malachite is always green, lapis lazuli always blue. These gems have a stable crystal structure that cannot be altered by heat or irradiation.
The majority of crystals, however, contain small imperfections and impurities within their chemical structures. Their colors then originate from these trace atoms that distort the crystal lattice and deflect or alter light rays as they pass through. For example, transparent quartz can appear violet when iron atoms are present, pink with titanium or manganese, and even smoky brown when subjected to natural radiation from uranium, intense gamma rays from space, or ultraviolet radiation from the sun. The beryl family includes green emeralds (chromium), yellow heliodor (iron), and pale rose to violet morganite (manganese). Green tourmaline (see our last issue on all tourmaline varieties) derives its color from sodium.
Many gemstones can be heat-treated or irradiated to enhance or change their color. The carefully heating of aquamarine will deepen its natural sea-green hue to sky or dark blue. Heated amethyst will turn yellow and resemble citrine. In fact, since this mineral is relatively rare, most citrine on the market today is heated amethyst.
Internal fractures and dislocations within a crystal lattice will also create beautiful plays of color and light so that a variety of color effects may be seen within a single crystal depending on the angle at which it is viewed. Examples may be found within tourmaline, aquamarine, morganite and labradorite.
