Glossary

Short, plain-language definitions of the terms used across Gemstonic.

Carat

The unit of gem weight, equal to 0.2 grams; not to be confused with karat, the measure of gold purity.

Inclusion

Any internal feature — a crystal, fracture or cavity — trapped inside a gem; inclusions affect clarity and can help identify a stone or reveal treatment.

Mohs scale

A 1–10 ranking of a mineral's scratch resistance, from talc (1) to diamond (10); each gem's hardness sets how well it survives daily wear.

Play-of-colour

The shifting spectral flashes seen in precious opal, caused by light diffracting through an ordered array of microscopic silica spheres.

Pleochroism

The property of showing different colours from different viewing directions, strong in gems such as tanzanite.

Refractive index

A measure of how much a gem bends light; higher values (like diamond's 2.42) generally mean more brilliance, and the value helps identify a stone.