Labradorite
At first glance, a piece of labradorite can look gray, dark, or fairly ordinary. Turn it toward the light, however, and brilliant flashes of blue, green, gold, orange, and sometimes purple or other colors can suddenly appear.
That remarkable optical effect is called labradorescence—and it is what makes labradorite one of the most recognizable and popular lapidary materials.
Labradorite — Learning Series 005 (PDF)
Optical Phenomena in Gemstones - Learning Series 004 (PDF)
What Is Labradorite?
Labradorite is a member of the feldspar group, one of the most abundant groups of minerals in Earth’s crust.
It was named for Labrador, Canada, where notable material was described in the 18th century. Labradorite is now found in several parts of the world, with important lapidary material coming from locations including Canada, Madagascar, Finland, and elsewhere.
Its appearance can vary considerably depending on its composition, internal structure, locality, and the way a piece is cut.
What Causes the Flash?
The colorful display in labradorite is not simply pigment within the stone.
As labradorite forms and cools, extremely fine internal structures can develop within the feldspar. Light interacting with these structures is reflected and interferes in ways that produce the colors we see.
This phenomenon is known as labradorescence. Learn more about labradorescence and other gemstone optical phenomena.
Because the effect depends on the angle between the stone, the light, and the viewer, the brilliant color may disappear completely when the stone is turned only a short distance.
Not Every Piece Flashes the Same Way
Labradorite can display a single strong color or several colors across the same stone. Blue and green are common, while strong yellows, oranges, reds, purples, and broad multicolor displays can be especially striking.
The amount of visible flash also varies. Some pieces produce a small patch of color, while others light up across most of their surface.
A beautiful piece of labradorite is therefore about more than simply having color. The strength, coverage, combination of colors, viewing angle, clarity, pattern, and quality of the finished polish can all affect its appearance.
Cutting Labradorite
Labradorite presents an interesting challenge for the lapidary.
Before cutting, the material needs to be examined from different directions to find the orientation that produces the best flash. A beautiful color display can be weakened—or nearly disappear—if the stone is cut at the wrong angle.
That makes orientation especially important.
Once the best viewing direction has been found, the cabochon can be designed so that its strongest labradorescence is visible from the face of the finished stone.
This is a great example of why cutting a cabochon involves more than simply shaping and polishing a rock. Sometimes the most important decision happens before the first cut is made.
Labradorite and Other Feldspars
Labradorite belongs to a large and sometimes confusing family of feldspar gemstones.
Moonstone, sunstone, and other feldspar varieties can also display interesting optical effects, but those effects are not all the same. Terms such as labradorescence, adularescence, and aventurescence describe different phenomena and should not be used interchangeably.
Understanding those differences makes the feldspar family even more interesting.
Learn more about Labradorite
Learn more in Learning Series 005 — Labradorite.
The guide takes a closer look at what labradorite is, what causes its remarkable color display, terminology, cutting considerations, and what to look for when examining a piece.
Labradorite — Learning Series 005 (PDF)
More Optical Phenomena to Explore
Labradorite is a wonderful introduction to the ways light can interact with gemstones.
Other materials can produce stars, cat’s-eyes, flashes, color changes, iridescence, and other effects—each with its own cause and terminology.
Sometimes the color you see in a gemstone isn’t really in the stone. It’s what happens when the stone meets the light.