Since most precious stones are small in size, in order to better observe the imperfections such as inclusions and fractures on the gemstones, microscopes and magnifying glasses are employed. A ..........

The refractive index is an important optical property of transparent gemstones and is also an important indicator of gemstone authentication. A refractometer measures the total internal refraction ..........

The dichroscope is the preferred type of instrument to inspect gemstones with pleochroisms. A calcite rhomb (Iceland spar) separates the polarized light rays that pass through the gemstones and ..........

A polariscope is composed of two polarized filters with their virational plane perpendicular to each other. When the vibrational plane of the polarizers is at right angles, light cannot pass ..........

The spectroscope is made up of a set of prisms, which breaks up the natural white light into a continuous visible spectrum (red, orange, yellow, green, blue, indigo and violet). A discontinuous ..........

Fluorescent light sources, while incapable of directly identifying gemstone types, are still effective tools used in authentication. Rubies and pyropes appear red under natural light; however when ..........

Built specifically to identify diamonds, this instrument measures the thermal conductance in gemstones. Since most gemstones lack or have very poor thermal conductivity, this instrument can ..........