Color shift is similar to color change, but more limited in scope. When exposed to different lighting environments, some gems will exhibit a small degree of change, generally within two adjacent colors of the visible light spectrum. The term color shift is used to describe this effect.

Tarnish is the undesirable dulling or discoloration of metals due to the effects of humidity, temperature, and other atmospheric conditions.

The term adamantine is used to describe any gemstone that has diamond-like luster. Only a few gems exhibit such exceptional light reflectance: cerrusite, sphalerite, and demantoid are three examples.

Adularescence is an optical phenomenon that manifests as a soft shimmer of light that moves within a gemstone as it is rolled back and forth. This property is most commonly associated with moonstone, a member of the feldspar family.

Agate is gemologically described as a cryptocrystalline variety of quartz. Rather than a single crystal, it is composed of myriad miniature crystals that can only be seen with extreme magnification. In appearance agate is often banded. The concentric bands may be oval, rounded, elliptical, or totally irregular in shape, and may be multiple colors, [..]

Named in honor of Czar Alexander II of Russia, alexandrite is actually a very special variety of the mineral chrysoberyl. It exhibits an exotic and highly prized optical property known as color change. When held in daylight, it appears greenish, but when held under the warm lights of candles or incandescent bulbs, it appears reddish. Even more exot [..]

An alloy is a mixture of two or more elements in solid solution in which the major component is a metal. Most pure metals are either too soft, brittle or chemically reactive for practical use. Combining different ratios of metals as alloys modifies the properties of pure metals to produce desirable characteristics. The aim of making alloys is gener [..]

Almandite is a member of the garnet group of gemstones. It is one of six species recognized by gemologists. The dominant hue is red, but the overall color may be modified by a little violet. Chemically it is an iron-aluminum silicate, but is rarely pure in nature. Almandite is very popular in jewelry since it is hard (7.5) and durable. Important so [..]

Amethyst is one of the better-known members of the quartz family. Color can range from soft lilac to intense purple or violet. Most amethyst is made by heating citrine, another member of the quartz family. Amethyst is popular in jewelry and serves as the birthstone for February. Important sources include Brazil, Madagascar, Mexico, Myanmar, Uruguay [..]

Ametrine is a bi-color variety of quartz. It is a combination of amethyst and citrine within a single crystal. The primary source of this gemstone is the Anahí mine in Bolivia. Read more about ametrine in our Gemopedia™. Shop Ametrine