Analysis:

Take tourmaline as an example:

Tourmaline is a common name of China's jewelry industry and belongs to the tourmaline family in mineralogy. The chemical molecular formula is XR3Al6B3Si6O27(OH)4, where X is Na, K and Ca, and R is various metal ions, and the type and content of R directly affect the color of tourmaline. It belongs to the tripartite crystal system. The crystal is a complex triangular column. There are various colors, such as colorless, rose red, pink, red, blue, green, yellow, brown and black, among which blue and fresh rose red are the top grades. Glass luster, transparent to translucent, refractive index is generally 1.624- 1.644, birefringence is 0.0 18-0.040, and dispersion is 0.0 17. It has a strong polychromatic color.

Visible multicolor is the color change caused by the different contents and types of trace metal ions or the change of crystal morphology in gemstones. It is discoloration caused by internal factors.

Color-changing effect refers to the phenomenon that gems show different colors under the influence of different external environments such as temperature, light and humidity. It is caused by external factors.