Labradorite

Mineral Name: Labradorite

Chemical Composition: (Ca,Na) (Si,Al)4O8, Sodium present can be (30-50%) and Calcium present can be (70-50%). (2)

Color: Labradorite is known for its labradorence because of the wonderful luminous colors it holds. You can often see, rainbow-like blues, yellows, greens, reds, and oranges. (2) However common findings of this mineral are usually flawed making it hard to see the colors and difficult to separate from other plagioclase minerals.

Streak: White (1)

Hardness: 6-6.5 (1)

Cleavage: Labradorite has 2 plains of cleavage at 90 degrees.

Crystal Form: Labradorite will rarely form in crystals but when it does they are usually tabular, which is a four-sided, thin crystal. Labradorite can also be twinned, meaning the crystal will form within itself creating a distinct, repeated pattern. (1)

Luster: Vitreous to Pearly

Special Features: Labradorite has a special feature called the Schiller Effect. The Schiller Effect is what gives the iridescence found in the mineral. This iridescence can be seen as the shine that is inside of the rock.

Varieties: Labradorite has three different varieties. Lynx Eye is a variety with green iridescence. Oregon Sunstone is a variety that contains natural copper in its composition making it have a copper-red hue. Finally, Spectrolite is a variety that has a strong schiller effect with intense colors (1).

Mineral Group: Labradorite is in the plagioclase series that is part of the Feldspar group. The plagioclase series is a group of feldspar minerals that contain calcium and sodium in their composition. The feldspar group also belongs to the aluminum silicates, which are minerals containing aluminum and the chemical silica (SiO2). This is a subdivision of silicates, which all contain silica. Labradorite also belongs to the tectosilicates, which are silicates where the oxygen atoms in silica are completely shared to form and three-dimensional network (1).

Environment: Labradorite is found in intrusive and extrusive igneous rocks. In Bowen’s reaction series you can find it forming in the basaltic rocks and maybe a little into andesitic rocks. It can also be found in metamorphic rocks that are metamorphosed from igneous rocks.

Associated Rock types: Labradorite is common in igneous rocks and has many forms. The coarse-grained rocks are granitoid, syenitoid, gabbroid, anorthositoid, foid-syenitoid and foid-gabbroid (4). The fine-grained rocks are trachytoid, andesitoid and tephritoid (4).

Occurrence in North America: Labradorite is super common in North America and can be found in the following states: Utah, Alabama, Arizona, Arkansas, California, Colorado, Connecticut, Georgia, Hawaii, Idaho, Maine, Massachusetts, Michigan, Minnesota, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Mexico, New York, North Carolina, Ohio, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, U.S. Virgin Islands, Utah, Vermont, Virginia, Washington, Wyoming. (5, 6)

Economic Uses: The most common economic use for labradorite is jewelry. The iridescence is what makes this a pretty gemstone. However, labradorite is very sensitive to impact making it difficult for mass production (2). Instead, this mineral is commonly turned into jewelry by jewelers who do custom work. Labradorite needs to be cut in a certain way for it to display the flash that many designers want their jewelry to have. This process of cutting includes four steps. First, you begin by identifying the part of the rock that shows the most flash. Second you investigate the angle of faces giving off the maximum flash. Third you square the mineral 90 degrees to the flash face so you can ensure a nice cut and last, you cut the mineral. (7)

Oregon Sunstone: Oregon Sunstone is a labradorite feldspar that contains native copper and also contains way more calcium than sodium in composition. It can display numerous colors, including being near-colorless to pale yellow to red and green, and also includes bicolor varieties (6). Oregon Sunstone is currently being mined in three different places in eastern Oregon: the Ponderosa mine in Harney County, and the Dust Devil and Sunstone Butte mines, both of which are about 120 miles further south, in Lake County (6). The cool thing about this variety of labradorite is that you can mine for it yourself. In Lake County, there is a mine that is to the public. A prospective miner can pay a certain amount of money to access the mine and whatever is found in the time period paid for is what can be kept.

First Notable Identification: Labradorite was first identified in Canada on the Isle of Paul which is near Nain, Labrador in 1770. (4)

How We Identified It: We identified it by the vibrant colors you can see within it when you rotate it. These colors are usually surrounded by a darker grey. If you’ve ever watched Dragon Tales, it looks like the egg.

Don’t Confuse It With: Labradorite could be confused with augite because of the similar look in rocks that they both occur in. However, the key is to look for the rainbow-like colors that hide in labradorite. Augite tends to be dark green in color and labradorite is blue.