Pleochroism occurs in varying degrees and is termed weak, distinct or strong. Among the gems that are strongly pleochroic are andalusite, iolite, kyanite, kunzite, sphene and tanzanite. Some pleochroic gems are said to be dichroic - displaying two different colors; kunzite is an example. Others are said to be trichroic, such as andalusite.

Pleochroism means "more colors." Pleochroic gems show two or three colors when viewed from different angles. This property appears quite spectacularly in gemstones such as andalusite, cordierite, emerald, and tanzanite. In gems such as peridot and aquamarine, it appears more subtly. Dichroic gems show two colors. Trichroic gems show three colors.

Gems are sometimes cut and set either to display pleochroism or to hide it, depending on the colors and their attractiveness. The pleochroic colors are at their maximum when light is polarized parallel with a principal optical vector. The axes are designated X, Y, and Z for direction, and alpha, beta, and gamma in magnitude of the refractive index.

Many gemstone properties stem from the crystal systems in which minerals form. The following gem structure table lists selected physical and optical characteristics based on mineral crystal systems, include characteristics of non-mineral amorphous gemstones.

The term pleochroism (from the Greek “pleio,” many, and “chros,” color) describes a variation of color with direction in doubly refractive gems (figure 1). Virtually all gemological texts note this effect and describe it in detail.

A description of pleochroism 79 linear absorption spectra as seen with a diffraction grating spectroscope. Last but not least the specific gravity, combined with the optical properties are very helpful to identify rough stones or sometimes double check cut stones.

Pleochroism is a fascinating optical phenomenon observed in certain gemstones and minerals. It refers to the ability of these materials to exhibit different colors depending on the viewing direction. This variation in color arises from the unequal absorption of light by the crystal structure.

A description of pleochroism: 79 linear absorption spectra as seen with a diffraction grating spectroscope. Last but not least the specific gravity, combined with the optical properties are very helpful to identify rough stones or sometimes double …

Pleochroism is an optical phenomenon where due to double refraction of light by a colored gem or crystal, the light is divided into two paths which are polarized at a 90° angle to each other. As the divided light follows different paths within the stone and are travelling at different speeds, they may have the result

Pleochroism is an optical phenomenon where due to double refraction of light by a colored gem or crystal, the light is divided into two paths which are polarized at a 90° angle to each other. As the divided light follows different paths within the stone and are traveling at different speeds, they may have the result of differential selective ...