Gemstone Glossary


See adularescence

Scissors cut

Mostly found in emerald cut stones, shows crossed, scissor-like crown facets. Often encountered in cheap (Verneuil) synthetics.

Scratch test

To determine the Mohs hardness of minerals, hardly used in gemmology which has to work non-destructively

Seal stone

Mostly oval or cushion shaped stone with slightly bevelled edge, used for engravings (mongrams, coats of arms etc.). Table can be flat or very slightly domed.


Transmitting some light only at thin edges

Shapes of cut

Most popular shapes:

Single refraction

Contrary to doubly refractive materials, singly refractive minerals do not split lightrays in two upon entry

Specific gravity

Density; the weight of a substance compared to the weight of an equal volume of water at 4°C


A square shaped stone, either step- or princess cut

Star effect

See asterism

Step cut

Style of cutting rectangular or octagonal stones with parallel facets arranged like steps of a staircase. The classic octagonal emerald cut is a step cut.

Synthetic gems

Mostly have the same chemical, physical and optical properties as their natural counterparts. As an example for an exception: synthetic spinels have a slightly higher refractive index than natural spinels.