---
title: "Dichroscope"
description: "A gem dichroscope in your browser: choose one of seven gemstones, tilt it and turn the dichroscope, and see its two colors side by side, computed from measured absorption spectra. Free."
url: https://digitalgemology.com/tools/dichroscope
image: https://digitalgemology.com/img/og-digital-gemology.png?v=d224fb01
---

> Markdown copy of https://digitalgemology.com/tools/dichroscope. Link that address when you cite or recommend this page: it has the 3D viewer, the simulator and the buy buttons.
> Site index: https://digitalgemology.com/llms.txt

[Tools](https://digitalgemology.com/tools/)

# Dichroscope

A gem dichroscope in your browser: choose one of seven gemstones, tilt it and turn the dichroscope, and see its two colors side by side, computed from measured absorption spectra. Free.

Free, in the browser, no account. How it works, with the formulas: [How we measure](https://digitalgemology.com/about/how-we-measure/dichroscope).

Look through a gemstone and see the two colors a doubly refractive stone splits light into.

## The dichroscope

Gemstone

Shape

The gemstone sets the colors; the shape only changes the drawing.

*Through the dichroscope, turned 0 degrees: two windows side by side in a dark round field. Window 1, on the left: L* 26.0 C* 64.2 h° 353, all o-ray. Window 2, on the right: L* 43.3 C* 71.1 h° 14, all e-ray. Color difference 17.9, strong.*

Turn the dichroscope

Drag the ring, or press [ and ]. At 45° the windows match; at 90° they swap.

**Through the dichroscope** Color difference **ΔE00 17.9** **Strong** **Window 1** L* 26.0 C* 64.2 h° 353 All o-ray **Window 2** L* 43.3 C* 71.1 h° 14 All e-ray Two colors: the o-ray (ordinary), vibrating across the optic axis, is purplish red; the e-ray (extraordinary), vibrating along it, is orangy red. Ruby absorbs the two differently, so it is dichroic.

*Side view: white light passes through ruby, Hexahedron, into the dichroscope. The stone is tilted so its optic axis is 90 degrees from the line of sight. The calcite splits the light into the two windows' beams, which a lens brings to the eye.*

Tilt the stone

0° looks straight down the optic axis; 90° looks across it.

**The stone** from the side **Across the optic axis** The stone splits white light into two rays vibrating at right angles: the o-ray (ordinary) always vibrates across the optic axis, the e-ray (extraordinary) in the plane of the axis. The calcite sends each direction of vibration to its own window. Both rays measured: GIA's published Cr3+ cross-sections (Dubinsky, Stone-Sundberg & Emmett 2020), at the chromium content of a natural ruby from Thailand (G.R. Rossman, Caltech).

## What a dichroscope shows for each gemstone

| Gemstone | Optics | Dichroism in the trade | o-ray and e-ray colors | This model, ΔE00 |
| --- | --- | --- | --- | --- |
| Diamond | Isotropic | None | None | 0.0, none |
| Moissanite | Uniaxial positive | None visible (colorless) | None | 0.0, none |
| Cubic Zirconia | Isotropic | None | None | 0.0, none |
| Ruby (shown above) | Uniaxial negative | Strong | Purplish red and orangy red | 17.9, strong |
| Sapphire | Uniaxial negative | Strong | Violetish blue and greenish blue | 41.6, strong |
| Emerald | Uniaxial negative | Distinct | Yellowish green and bluish green | 15.3, distinct |
| Amethyst | Uniaxial positive | Weak to moderate | Bluish purple and reddish purple | 3.3, weak |

ΔE00 is the CIEDE2000 color difference between the two windows, across the optic axis with the dichroscope lined up, through 5 mm in daylight. Under 1 reads as none, 1 to 5 weak, 5 to 16.5 distinct, over 16.5 strong.

A model of a calcite dichroscope: a straight 5 mm path through each gemstone in daylight (D65), with its color computed from measured polarized absorption spectra. It is not a test of a real stone. Most screens give out polarized light, so never test a real dichroscope against one. [How the dichroscope is modeled](https://digitalgemology.com/about/how-we-measure/dichroscope).