Inclusions can end up in gemstones in several ways:
- they have formed prior to their host (protogenetic) which grew around them.
- they have formed together with the host (syngenetic).
- they have formed after the host developed (epigenetic).
A Slender, Double Refractive, Crystal of Unknown Composition Causes a Beautiful Image When it’s Host, a Garnet, is Placed in Between Crossed Polars.
Image by Tim Spauwen.
This Zircon Crystal in a Sapphire Gives a Strong Suspicion that its Host has Been Heated by Showing Us a Stress Fracture Around it.
Image by Tim Spauwen
Edward Gübelin and John Koivula are two preeminent gemologists who have published a series of indispensable books on inclusion studies that every gem fanatic should read: Photoatlas of Inclusions in Gemstones, Volumes 1, 2 & 3.