Lesson 4: Identifying Inclusions of Specific Gems

Step 2: Advanced Gemology

Lesson 12

identifying inclusions - blue gemstone

Beryl and Tourmaline

Both beryl and tourmaline develop hollow or “growth” tubes. Gem cutters see many more of these than gemologists do, since they cut away most of these inclusions. While these tubes begin hollow, they may be filled with opaque, white minerals later, as the crystal develops.

You can easily distinguish growth tubes from other inclusions. They have even sides and run straight for considerable distances. When present, you can assume these inclusions indicate a gem is most likely a beryl, tourmaline, or possibly spodumene. A refractive index (RI) reading can then distinguish these minerals.


Rubies and sapphires, both corundum gemstones, are some of the easiest gems to identify by their inclusions.

Silk in Hexagonal Patterns

Silk is the most distinctive of corundum’s inclusions. What gemologists call “silk” consists of very fine threads (crystals) of another mineral, …

Unearth The Secrets Behind The Beauty

Introducing "Discover Gemology" by IGS, the premiere introductory training for those fascinated by the magnificent world of gemology.

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