Polariscope Analysis

Overview

The polariscope determines a gem's optical character (singly or doubly refractive), detects strain, and can help identify aggregate materials and certain treatments.

How It Works

Two polarizing filters are crossed at 90°, blocking light. When a doubly refractive gem is placed between them, it appears light and dark as rotated. Singly refractive gems remain dark.

Equipment Needed

• Polariscope (two polarizing filters)
• Light source
• Conoscope lens (optional for optic figure)
• Gem holder

Procedure

1. Cross the polarizers until the field is dark
2. Place the gem between the filters
3. Rotate the gem 360° and observe changes
4. If gem stays dark: singly refractive
5. If gem blinks light/dark 4 times: doubly refractive
6. Use conoscope for optic figure if doubly refractive

Typical Values / Results

Gemstone	Value / Observation
Singly Refractive	Diamond, spinel, garnet (stays dark)
Doubly Refractive	Sapphire, emerald, quartz (blinks 4x)
Aggregate/Polycrystalline	Jade, chalcedony (stays light)
Strained	Shows anomalous double refraction

Limitations

Small gems are difficult to observe. Strain can cause singly refractive gems to appear doubly refractive. Practice required.