Lesson 3: Understanding Gemological Formulas

Step 1: Introduction to Gemology

Lesson 3

The chemical composition of a mineral is a primary aspect of its definition as a species. That composition can be expressed in a chemical formula that identifies the elements and proportionate number of atoms in a molecule or chemical compound of that mineral. Gemological formulas are chemical formulas of gems and other minerals of interest in the world of jewelry and gem collecting. For example, quartz has a chemical formula of SiO2, one atom of silicon to two atoms of oxygen.


Many gemological formulas contain elements grouped in parentheses with commas, for example (Fe, Mg). This indicates that either iron (Fe) or magnesium (Mg), or both, may occupy a specific position in the crystal structure. The element listed first within a parenthesis is the one present in a greater amount on the structural site. In some cases …

Unearth The Secrets Behind The Beauty

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  • How to spot the most unique & valuable characteristics of different gemstones
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Course: Discover Gemology: Fundamentals, Tools & Meanings
Purchase Course: $49
Skill Level: beginnner
Lessons: 48
Time: 480 min