1. Turn the analyzer (top) filter so that light is blocked.

2. The gem should allow light to pass through—it can even be a rough stone. Avoid using opaque gems or those set in a closed setting.

3. Place the gem on the polarizer (bottom) filter.

4. Rotate the gemstone by turning the bottom filter or using your tweezers.

• If the gem stays dark while rotating, it is isotropic (e.g., Garnet, Spinel).

• If it "blinks" between light and dark four times during a full rotation, it is anisotropic (e.g., Beryl, Topaz).

• If it remains bright throughout, it is polycrystalline anisotropic (e.g., Jadeite Jade, Chalcedony Quartz).

1. Block the light coming through the polariscope, then place the gem under it.

2. Use an anisotropic gemstone that allows light to pass through.

3. Hold the gem with tweezers and slowly move it until you see some iridescent, rainbow-like shimmering.

4. At that spot, gently touch the gemstone with the conoscope—you should see an interference figure appear.

5. It will be one of three types:

   • Biaxial – Appears as a wide bowtie or two curved dark bands.

   • Uniaxial – Looks like a target: concentric circles with a cross in the center.

   • Bullseye – A quartz-only variation of the uniaxial pattern, featuring a glowing, iridescent center instead of a cross.

1. Use a flat light and a “London” dichroscope.

2. Choose a colored, anisotropic gemstone that allows light to pass through.

3. Hold and move both the gem and the dichroscope at different angles—up and down, left and right.

4. Watch for any color changes between the two half-centered filters of the dichroscope.

5. If the gemstone shows two distinct colors side by side, it exhibits pleochroism—a phenomenon where the gem displays different colors when viewed from different angles under the same light.

The gemstone should be faceted or a cabochon, not rough, as rough stones can scratch the glass surface.

Refractive liquid is toxic, so handle it with care and follow the safety instructions.

1. Place a tiny drop of refractive liquid on the glass surface.

2. Clean the gem with a soft cloth and ently place it on top of the drop.

3. Look through the viewfinder to check the shadow line—it indicates the refractive index (RI).

• If the gem is isotropic, you'll see only one consistent value.

• If it’s anisotropic, you’ll see two values as you rotate the polarizing filter on the viewfinder.

When this occurs, make a note of the readings. Then, gently rotate the stone about 45 degrees and repeat the process a total of four times.

• The lowest RI and the highest RI are the LoRI and HiRI, respectively.

• The difference between them is the gem’s birefringence.

When you're done, clean everything thoroughly—wipe the gemstone and the surface of the refractometer.

Bonus tip: If one RI remains steady while the other changes, the stone is uniaxial. If both change, it’s biaxial.

This method is suitable for gemstones over 1 carat in weight.

Set up the hydrostatic balance kit on your scale according to the instructions.

You should end up with a setup where a water container is suspended above the scale, but its weight is not registered by the scale. A tray is submerged in the water, and only this tray is weighed by the scale.

The water should sit around or next to the scale, effectively bypassing it.

Make sure the submerged tray isn’t touching anything, and that the support cage rests cleanly and stably on the scale.

Set the scale to carats, and zero it out.

1. First, weigh the gem in air. Repeat a few times for accuracy.

2. Then gently place the gem on the tray underwater.

3. Record the reading and remove the gem.

4. Repeat this underwater measurement 3–4 times to ensure consistency.

Important tips:

• Wipe off any water from the gem and tweezers before each weigh-in.

• Watch for air bubbles trapped under the gemstone—they’ll throw off the reading.

Once both weights are consistent, use this formula to calculate specific gravity:

Specific Gravity = Weight in Air ÷ (Weight in Air – Weight in Water)