Gemology Glossary Flashcards

Flashcards for reviewing gemology terms and definitions from lecture notes.

ABSORB, ABSORPTION (light)

Visible light interacts with electrons in a material, converting it into heat energy, preventing its transmission through the material.

ABSORPTION SPECTRUM

A pattern of dark bands or lines in the visible light spectrum observed through a spectroscope when viewing light from certain gem materials.

ADAMANTINE LUSTRE

A very bright and reflective lustre, typically displayed by diamond.

ALLOCHROMATIC

Materials that owe their body color to chemical elements not essential to their composition.

ALLUVIAL DEPOSIT

Sedimentary rock deposit formed by water eroding and transporting rock material, often containing placer deposits or gem gravels.

AMORPHOUS

A material with randomly-oriented atoms, molecules, or minute crystalline sectors, exhibiting no overall crystal form or effects.

ANALYSER

The upper polarizing filter fitted to polariscopes and certain types of microscope.

ANGSTRÖM

Unit of length measurement for wavelengths of certain ranges of electromagnetic radiation, now largely superseded by the nanometre (nm).

ANISOTROPIC

A material which exhibits different optical properties in different directions.

ANOMALOUS EXTINCTION EFFECT ('anomalous birefringence')

A pattern of light and dark extinction zones when viewing gemstones between crossed polarizers, caused by internal strain.

ARCHIMEDES' PRINCIPLE

An object immersed in a fluid experiences an upward force equal to the weight of the fluid it displaces.

ARTIFICIAL

Not natural or naturally-formed; 'man-made'.

CONCHOIDAL FRACTURE

A fracture with no cleavage plane that results in a curved break with concentric ridges, resembling the markings on a seashell

ULTRAVIOLET FLUORESCENCE

A method of identifying gemstones by their reactions to ultraviolet (UV) radiation. Some gemstones fluoresce (emit visible light) when exposed to UV light, while others do not.

SPECTROSCOPE

An instrument used to observe the spectrum of light emitted by a gemstone. It helps in identifying the chemical elements present in the gemstone.

REFRACTION

The bending of light as it passes from one medium to another. This property is responsible for the brilliance and fire of gemstones.

CRITICAL ANGLE

The angle at which light is totally internally reflected within a gemstone. This angle is critical for the gemstone's brilliance.

BRILLIANCE

A measure of how well a gemstone returns light to the viewer's eye. A well-cut gemstone will have a high brilliance rating.

FIRE

The flashes of color seen in a gemstone due to dispersion. Diamond is known for its high fire.

TYNDALL EFFECT

The scattering of light by particles in a gemstone. This effect can create a hazy or milky appearance.

COLOR CHANGE

A phenomenon where certain gemstones appear to change color under different light sources, such as daylight and incandescent light.

Defects or inclusions within a gemstone that affect its clarity