Color is one of the most eye-catching feature of many minerals. Some minerals always have the same color, such as gold, whereas some minerals, such as quartz and calcite, come in all colors. The presence and intensity of certain elements determines a specimens color. Minerals with an inherent color (i.e. all specimens of the mineral are the same color) have essential elements in them which cause their color. Good examples are azurite and malachite, which have their strong blue and green color due to their copper in their atomic structure. But there are many minerals which have slight additions of color-causing elements in some specimens that cause it to be a different color. For example, pure quartz (SiO₂), is colorless, whereas amethyst, a purple variety of quartz, has its purple color caused by traces of iron. The amount of iron present determines the intensity of the color.

Certain minerals exhibit a color change when exposed to light, heat, or radiation. Realgar transforms into orpiment, and orpiment crumbles into a light-yellow powder if exposed to light. Some minerals, such as proustite and vivianite, darken upon prolonged exposure to light, whereas other minerals, such as kunzite fade. Some minerals undergo color changes when put under intense heat. This method is sometimes used to artificially enhance the color of some gemstones. Some varieties of topaz, beryl, and corundum are heat treated to produce deep colored gemstones from rather dull ones. Radioactivity can also have an effect, as is the cause of smoky quartz.

Most secondary copper minerals show a bright blue (and sometimes green) color. Iron usually causes a mineral to exhibit a dark red or brown color, and manganese is responsible for the coloring of many pink minerals. Some minerals, such as cassiterite and zincite, have chemical structures that would cause them to be colorless, but due to impurities they are never found colorless. Most secondary uranium minerals exhibit either a bright neon yellow or green color. Often, a mineral is coated or "pseudomorphed", causing it to exhibit the color of the replaced or coated mineral. Two common examples are: hematite coating quartz, and limonite pseudomorph after pyrite.

Minerals containing the elements aluminum, sodium, and potassium are usually colorless or very lightly colored. In some cases, the color of a mineral may depend on its atomic bonding rather than composition, such as by diamond and graphite. Both these minerals have the same are formed from the same material (carbon), yet one is almost always white or very lightly colored, while the other is dark gray to black.

Many times, minute traces of a mineral in or over another mineral can cause a color change. Two fine examples are:
1) Malachite on quartz, causing the quartz appear to be green.
2) Rutile inclusions in quartz, giving the quartz a golden hue.

Several minerals tarnish, thereby affecting their color. The best examples are:
1) Silver, which tarnishes black, yellow, or brown
2) Copper, which tarnishes green
3) Bornite and chalcopyrite, which tarnish an iridescent play of colors

Some minerals, such as opal, display a multicolored effect when viewed from different angles. This is called opalescence. A few minerals appear to change color when viewed in different light. Alexandrite, a variety of chrysoberyl, is dark green in natural light, but takes on a purplish hue in artificial light. Other minerals will change color when viewed at different angles. This is called dichroism or pleochroism. Cordierite, the most famous dichroic mineral is bluish-purple but turns gray when rotated or viewed at a different angle. The properties of opalescence, labradorescence, and dichroism, as well as other optical properties are explained in greater detail in the section "Other Properties".

Mineral colors may be artificially enhanced in various ways. This includes heating and irradiation (both previously mentioned), as well as dying. A few minerals, especially agates, are periodically dyed to enhance their color.

How to use color as an identification mark

Color alone will not normally identify a mineral, but it can be a very helpful factor. Many minerals come in a great diversity of colors, and many different minerals have similar colors. However, a few minerals can be identified solely by their color (usually in addition to crystal shape), for example azurite, wulfenite, and dioptase. Such minerals are known as monochromatic minerals.

Together with color, a crystal shape can identify most of the better known minerals. It is best to observe the mineral in strong light, preferably daylight. Make sure not to observe a tarnished or discolored surface. One more thing to bear in mind is that some minerals can have a questionable color. Some may think that it is one color, while others may think it is a different color.

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