Gem Structure Chart
A gem structure chart that shows various information on a specific structure and gems of example. Details include Refractive Indexes, Pleochroism and etc.
By International Gem Society, updated on
| Structure | Crystal axes and Angles | Optic Character | Refractive Indexes | Optic Sign | Pleochroism | Examples |
| Amorphous | No orderNo axes | IsotropicSingly refractive | 1 RI | None | None | Opal, Amber, Glass, Plastic |
| Isometric | 1 axis lengthAll at 90° | IsotropicSingly refractive | 1 RI | None | None | Diamond, Spinel, Garnet |
| Tetragonal | 2 axis lengths All at 90° | AnisotropicDoubly refractive | 2 RI's | Uniaxial | May be dichroic | Zircon |
| Hexagonal | 2 axis lengths | AnisotropicDoubly refractive | 2 RI's | Uniaxial | May be dichroic | Quartz, Beryl, Apatite, Corundum, Tourmaline |
| Orthorhombic | 3 axis lengthsAll at 90° | AnisotropicDoubly refractive | 3 RI's | Biaxial | May be trichroic | Topaz, Zoisite, Peridot |
| Monoclinic | 3 axis lengths 2 axes at 90°; 1 oblique | AnisotropicDoubly refractive | 3 RI's | Biaxial | May be trichroic | Orthoclase, Spodumene |
| Triclinic | 3 axis lengths all axes oblique | AnisotropicDoubly refractive | 3 RI's | Biaxial | May be trichroic | Labradorite, Axenite |
GEM STRUCTURE CHART
Compliments ofThe International Gem Society
International Gem Society
Related Articles
Gemstone Toxicity Table
Gem faceters and jewelry enthusiasts alike should learn about gemstone toxicity. This table has toxicity ratings for 280+ gems, based...
Read More
Standard Gem Sizes Chart
Will your gem fit in a standard setting? Use this chart of standard gem sizes for popular cuts and also...
Read More
METAL/WAX FORMULAS
Jewelers need to know how to determine how much gold is needed for a wax mold. Here are three methods...
Read More
The Mohs Hardness Scale and Chart for Select Gems
The Mohs hardness scale measures a mineral's resistance to scratching. Find the traditional scale here and a chart of select...
Read More
Latest Articles
A Guide to Early Victorian Romantic Period Jewelry
The Romantic Period marked the start of the Victorian Era. Learn about the typical qualities of Romantic Period jewelry, including...
Read More
Malaya or Malaia Garnet Value, Price, and Jewelry Information
Malaia or malaya garnets are typically light to dark, slightly pinkish orange, reddish orange, or yellowish orange in color. This...
Read More
Choosing Your First Gemstones: A Rough Guide for Faceters
How should novice faceters choose their first gemstones? Learn which gem rough materials combine cutting ease, low cost, good size,...
Read More
Gemstone Coatings: CVD and More
Gemstone coatings are a simple way to enhance color and luster. Learn about commonly coated gems, different coating techniques, and...
Read More
Never Stop Learning
When you join the IGS community, you get trusted diamond & gemstone information when you need it.
Get Gemology Insights
Get started with the International Gem Society’s free guide to gemstone identification. Join our weekly newsletter & get a free copy of the Gem ID Checklist!