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
- Cross the polarizers until the field is dark
- Place the gem between the filters
- Rotate the gem 360° and observe changes
- If gem stays dark: singly refractive
- If gem blinks light/dark 4 times: doubly refractive
- Use conoscope for optic figure if doubly refractive
🔍 What You'll See: Optical Character Guide
When rotating a gem 360° between crossed polarizers, here's what each result means:
| Optical Character | What You'll See | Examples |
|---|---|---|
| Singly Refractive | The gem stays COMPLETELY BLACK the entire 360° turn. No flashing, no lightening, just solid darkness throughout. If you see ANY light coming through at any point, it's not singly refractive. | Diamond, Garnet, Spinel, Glass |
| Doubly Refractive | As you rotate, the gem goes: BLACK → bright → BLACK → bright → BLACK → bright → BLACK → bright. Exactly 4 times it goes dark during one full turn. The bright moments show colors or white light passing through. | Ruby, Sapphire, Emerald, Tourmaline, Peridot |
| Aggregate | The gem looks like TV static or a fuzzy grey mess. You'll see tiny bright and dark speckles mixed together that shimmer and shift as you rotate – like glitter in concrete. Never goes fully dark or fully bright. | Jade (jadeite/nephrite), Chalcedony, Lapis Lazuli |
| Anomalous DR | Instead of clean blinks, you see weird patchy blobs of light and dark that look like snakeskin, zebra stripes, or a tabby cat pattern. The light areas seem to crawl or shift position as you rotate. This is caused by internal stress. | Some Garnets (especially Almandine), stressed Diamonds |
| Variable | Flip the gem on its side and test again. In one direction it may stay dark (like SR), but rotate it 90° and suddenly it blinks 4 times (like DR). The result changes based on which direction you're looking through. | Looking down the optic axis of uniaxial gems like Quartz |
| Amorphous | Same as singly refractive: stays COMPLETELY BLACK the whole rotation. These materials have no crystal structure at all, so light passes straight through without bending. Totally dark, no exceptions. | Opal, Amber, Obsidian, Glass |
| Unknown | The gem is too small, too dark, or too included to get a clear reading. Try better lighting, a cleaner stone, or a different angle. If still unclear, use other tests like refractive index or specific gravity. | Very small gems, heavily included stones, opaque materials |
💡 Beginner's Tip: Count how many times the gem goes dark as you rotate it one full turn.
Four "blinks" (dark spots) = doubly refractive. Stays dark the whole time = singly refractive.
Typical Values / Results
| Gemstone | Optical Character |
|---|---|
| Diamond | Singly refractive |
| Alexandrite | Doubly refractive |
| Emerald | Doubly refractive |
| Paraiba Tourmaline | Doubly refractive |
| Musgravite | Doubly refractive |
| Painite | Doubly refractive |
| Taaffeite | Doubly refractive |
| Ruby | Doubly refractive |
| Red Spinel | Singly refractive |
| Bixbite | Doubly refractive |
| Grandidierite | Doubly refractive |
| Sapphire | Doubly refractive |
| Tanzanite | Doubly refractive |
| Blue Spinel | Singly refractive |
| Imperial Topaz | Doubly refractive |
| Serendibite | Doubly refractive |
| Vayrynenite | Doubly refractive |
| Benitoite | Doubly refractive |
| Demantoid | Singly refractive |
| Tsavorite | Singly refractive |
| Padparadscha Sapphire | Doubly refractive |
| Clinohumite | Doubly refractive |
| Afghanite | Doubly refractive |
| Jeremejevite | Doubly refractive |
| Pink Spinel | Singly refractive |
| Pink Topaz | Doubly refractive |
| Sphene | Doubly refractive |
| Rubellite | Doubly refractive |
| Indicolite | Doubly refractive |
| Sphalerite | Singly refractive |
| Hiddenite | Doubly refractive |
| Diaspore | Doubly refractive |
| Andradite | Singly refractive |
| Watermelon Tourmaline | Doubly refractive |
| Andalusite | Doubly refractive |
| Kunzite | Doubly refractive |
| Aquamarine | Doubly refractive |
| Morganite | Doubly refractive |
| Heliodor | Doubly refractive |
| Goshenite | Doubly refractive |
| Green Beryl | Doubly refractive |
| Cat's Eye Chrysoberyl | Doubly refractive |
| Star Sapphire | Doubly refractive |
| Star Ruby | Doubly refractive |
| Moonstone | Doubly refractive |
| Labradorite | Doubly refractive |
| Sunstone | Doubly refractive |
| Amazonite | Doubly refractive |
| Orthoclase | Doubly refractive |
| Andesine | Doubly refractive |
| Oligoclase | Doubly refractive |
| Black Opal | Amorphous |
| Fire Opal | Amorphous |
| Crystal Opal | Amorphous |
| Boulder Opal | Amorphous |
| White Opal | Amorphous |
| Jelly Opal | Amorphous |
| Hyalite | Amorphous |
| Peruvian Opal | Amorphous |
| Amethyst | Doubly refractive |
| Citrine | Doubly refractive |
| Rose Quartz | Doubly refractive |
| Smoky Quartz | Doubly refractive |
| Ametrine | Doubly refractive |
| Prasiolite | Doubly refractive |
| Milky Quartz | Doubly refractive |
| Rock Crystal | Doubly refractive |
| Rutilated Quartz | Doubly refractive |
| Tourmalinated Quartz | Doubly refractive |
| Aventurine | Doubly refractive |
| Tiger's Eye | Doubly refractive |
| Hawk's Eye | Doubly refractive |
| Chalcedony | Doubly refractive |
| Agate | Doubly refractive |
| Carnelian | Doubly refractive |
| Chrysoprase | Doubly refractive |
| Onyx | Doubly refractive |
| Sardonyx | Doubly refractive |
| Bloodstone | Doubly refractive |
| Jasper | Doubly refractive |
| Peridot | Doubly refractive |
| Zircon | Doubly refractive |
| Rhodolite | Singly refractive |
| Almandine | Singly refractive |
| Pyrope | Singly refractive |
| Spessartite | Singly refractive |
| Grossular | Singly refractive |
| Uvarovite | Singly refractive |
| Mali Garnet | Singly refractive |
| Color-Change Garnet | Singly refractive |
| Rhodochrosite | Doubly refractive |
| Iolite | Doubly refractive |
| Kyanite | Doubly refractive |
| Kornerupine | Doubly refractive |
| Seraphinite | Doubly refractive |
| Charoite | Doubly refractive |
| Sugilite | Doubly refractive |
| Larimar | Doubly refractive |
| Jadeite | Doubly refractive |
| Nephrite | Doubly refractive |
| Lapis Lazuli | Aggregate |
| Turquoise | Doubly refractive |
| Malachite | Doubly refractive |
| Azurite | Doubly refractive |
| Rhodonite | Doubly refractive |
| Sodalite | Singly refractive |
| Prehnite | Doubly refractive |
| Fluorite | Singly refractive |
| Apatite | Doubly refractive |
| Scapolite | Doubly refractive |
| Diopside | Doubly refractive |
| Enstatite | Doubly refractive |
| Hypersthene | Doubly refractive |
| Burmese Spinel | Singly refractive |
| Tanzanian Spinel | Singly refractive |
| Vietnamese Purple Spinel | Singly refractive |
| Quartz | Doubly refractive |
| Serpentine | Doubly refractive |
| Aragonite | Doubly refractive |
| Black Diamond | Singly refractive |
| Phenakite | Doubly refractive |
| Verdelite | Doubly refractive |
| Tourmaline | Doubly refractive |
| Topaz | Doubly refractive |
| Opal | Amorphous |
| Spinel | Singly refractive |
| Garnet | Singly refractive |
| Pink Diamond | Singly refractive |
| Yellow Diamond | Singly refractive |
| Brown Diamond | Singly refractive |
| Chrysoberyl | Doubly refractive |
| Danburite | Doubly refractive |
| Tantalite | Doubly refractive |
| Bastnasite | Doubly refractive |
| Xenotime | Doubly refractive |
| Erythrite | Doubly refractive |
| Scheelite | Doubly refractive |
| Cassiterite | Singly refractive |
| Hackmanite | Singly refractive |
| Hauyne | Singly refractive |
| Poudretteite | Doubly refractive |
| Spodumene | Doubly refractive |
| Malaya Garnet | Singly refractive |
| Mahenge Spinel | Singly refractive |
| Pezzottaite | Doubly refractive |
| Green Diamond | Singly refractive |
| Blue Diamond | Singly refractive |
| Chrome Sphene | Doubly refractive |
| Blue Topaz | Doubly refractive |
| Feldspar | Doubly refractive |
| Opaque Emerald | Doubly refractive |
| Opaque Hauyne | Singly refractive |
| Hematite | Doubly refractive |
| Cuprite | Singly refractive |
| Cerussite | Doubly refractive |
| Calcite | Doubly refractive |
| Smithsonite | Doubly refractive |
| Brazilianite | Doubly refractive |
| Amblygonite | Doubly refractive |
| Bytownite | Doubly refractive |
| Pollucite | Singly refractive |
| Petalite | Doubly refractive |
| Phosphophyllite | Doubly refractive |
| Dioptase | Doubly refractive |
| Achroite | Doubly refractive |
| Albite | Doubly refractive |
| Elbaite | Doubly refractive |
| Axinite | Doubly refractive |
| Vesuvianite | Doubly refractive |
| Epidote | Doubly refractive |
| Zoisite | Doubly refractive |
| Sillimanite | Doubly refractive |
| Euclase | Doubly refractive |
| Moldavite | Amorphous |
| Beryl | Doubly refractive |
| Triplite | Doubly refractive |
| Sapphirine | Doubly refractive |
| Pargasite | Doubly refractive |
| Hambergite | Doubly refractive |
| Parisite | Doubly refractive |
| Idocrase | Doubly refractive |
| Herderite | Doubly refractive |
| Chondrodite | Doubly refractive |
| Stibiotantalite | Doubly refractive |
| Chrome Tourmaline | Doubly refractive |
| Rhodizite | Singly refractive |
| Hessonite | Singly refractive |
| Color Change Garnet | Singly refractive |
| Color Change Sapphire | Doubly refractive |
| Hydrogrossular | Singly refractive |
| Ammolite | Aggregate |
| Amber | Amorphous |
| Lepidolite | Doubly refractive |
| Brucite | Doubly refractive |
| Mawsitsit | Aggregate |
| Hemimorphite | Doubly refractive |
| Fire Agate | Doubly refractive |
| Synthetic Sapphire | Doubly refractive |
| Synthetic Ruby | Doubly refractive |
| Synthetic Emerald | Doubly refractive |
| Synthetic Moissanite | Doubly refractive |
Limitations
Small gems are difficult to observe. Strain can cause singly refractive gems to appear doubly refractive. Practice required.