Mother of pearl's iridescence is caused by light interference across aragonite platelets so thin they diffract individual wavelengths, scattering them differently as the viewing angle changes, which produces the shifting color effect.
Visually Speaking
Enamel's palette is structurally separate from the gemstone world. Metal oxides in glass rather than mineral crystal formation produce the opaque whites, deep blacks, and saturated primary colors that give jewelry designers a large color range that no stone selection duplicates.
Quality & Value
Fine jewelry-quality hardness, excellent natural clarity, and a color range from vivid blue to rare imperial orange-pink, allows topaz gift buyer value to rest on properties that hold across the full category rather than concentrating in a single variety.