Gem Structure and Classification

  • How do chemical composition and crystal structure determine a gem’s identity?
  • What features help classify gems?
  • What makes a mineral part of a group?
  • What are some ethical ways to describe laboratory-grown gems?

An introduction to the world of colored stones wouldn’t be complete without a discussion of some gem structure and classification basics. Chemical composition—the kinds and relative quantities of a gem’s atoms—and crystal structure—the arrangement of those atoms—are the factors that determine a gem’s identity. They also determine how gems are classified into specific categories.

It’s also important to know about lab-grown gems and some of the ways you can ethically describe them. This subject is covered in more detail in Assignment 5, but a brief introduction in this section will equip you for quick entry to the selling floor.