Fluid Inclusions

Two-phase, three-phase, and negative crystal inclusions - trapped fluids that reveal formation conditions.

microscopy identification origin fluids

Introduction

Fluid inclusions are cavities containing liquids, gases, or combinations trapped
during crystal growth. They provide crucial information about the conditions under
which the gem formed and are often diagnostic for origin determination.

Types of Fluid Inclusions

Single-Phase Inclusions

Contain only one phase (liquid or gas):

  • Liquid-filled - Cavities filled with liquid only
  • Gas-filled - Rare, usually in volcanic-origin gems
  • Typically smaller than multi-phase inclusions

Two-Phase Inclusions

The most common type, containing liquid and a gas bubble:

  • Appearance: Liquid-filled cavity with a mobile gas bubble
  • Behaviour: Bubble moves when stone is tilted
  • Common in: Topaz, aquamarine, tourmaline, spinel
  • Identification value: Confirms natural origin

Three-Phase Inclusions

Contain liquid, gas, and a solid crystal - highly diagnostic:

  • Components: Liquid + gas bubble + solid crystal (often halite)
  • Classic example: Colombian emerald (jagged cavity with halite cube)
  • Diagnostic value: Often origin-specific
  • Also seen in: Some quartz, topaz, spinel

Colombian Emerald Three-Phase

Negative Crystals

Negative crystals are fluid-filled cavities that have the geometric shape of the
host mineral's crystal structure:

  • Formation: Cavity walls follow crystal structure
  • Shape: Reflects host mineral's crystal habit
  • Examples:
    • Octahedral negative crystals in spinel
    • Hexagonal negative crystals in beryl
    • Rhombohedral negative crystals in quartz

Fluid Inclusions by Gemstone

Characteristic Fluid Inclusions
Gemstone Typical Fluid Inclusions Diagnostic Features
Emerald Two-phase, three-phase Colombian: three-phase with halite
Aquamarine Two-phase, rain-like tubes Parallel elongated inclusions
Topaz Two-phase Elongated cavities
Spinel Negative crystals, fingerprints Octahedral shapes
Tourmaline Two-phase, growth tubes Parallel to c-axis
Quartz Two-phase, three-phase Can show moving bubbles

Emerald Fluid Inclusions by Origin

Emerald fluid inclusion characteristics vary significantly by geographic origin:

Colombian

  • Three-phase inclusions (diagnostic)
  • Jagged cavity walls
  • Halite cubes in fluid
  • "Jardin" garden-like appearance

Zambian

  • Two-phase inclusions dominant
  • Blocky fluid cavities
  • Less halite, more biotite
  • Generally cleaner appearance

Brazilian

  • Two-phase inclusions
  • Biotite mica common
  • Pyrite crystals
  • Chromite occasionally

Moving Bubble Test

Some fluid inclusions contain mobile gas bubbles that can be observed moving:

Observation technique:

  1. Place gem under microscope
  2. Locate two-phase inclusion with visible bubble
  3. Gently tilt the stone
  4. Observe bubble movement within cavity

Significance:

  • Confirms liquid-filled cavity (not solid)
  • Natural feature (synthetics rarely show this)
  • Documents inclusion type accurately

Treatment Indicators

Related Topics

Inclusions OverviewSolid Inclusions