LABRADORITE
A Feldspar Mineral with a Rainbow Inside
Collectors o en dig labradorite as a colorful rock, but it is actually a mineral, not a rock. It is one of a half dozen varieties of feldspar divided into two groups that make up the crust of the earth. One group is the potassium feldspars, including microcline. e other group is a plagioclase feldspar, including labradorite.
Labradorite occurs in two forms, massive rock outcrops useful in construction and lapidary work. It is also found in small crystalline and gemmy phenocrysts in volcanic rock suitable for faceted jewelry. It is most often found as huge rock masses that outcrop in areas as part of huge plutonic intrusive formations. These rock-like masses of labradorite often show various colors that flashback at the viewer when the rock is tilted and moved. The crystalline gem phenocrysts are much less common and can be a variety of colors. With a hardness of six to six and one-half, they can be used as faceted gemstones when properly set.
The remarkable play of colors seen in massive labradorite is predominantly blue, but flashes of bronze, golden, red, green and yellow show up as a piece is rotated or moved under a strong light source. Both exciting massive and gemmy types of labradorite can be self-collected. Outcrops of massive labradorite are found in a host of countries, including the United States, where it has been mined as a decorative stone for carvings and less often for jewelry.
CANADIAN DISCOVERY
Massive labradorite was first collected on the Isle of Paul, near Nain, Labrador, Canada, hence the name for this calcium, sodium aluminum silicate. There are other nearby Labrador sources, but the material from near Nain collected in 1770 created quite a stir. The specimens collected showed a remarkable play of colors that excited scientists and triggered a search for more such beauty. It was later found in even more spectacular form in Tvedestrand, Kragero, Norway and surrounding environs. Finland yielded the most spectacular labradorite at Ylamoa, Lammenpa. Some pieces were so colorful as to be called spectrolite. Later, Russia and elsewhere produced equally exceptional labradorite.
What makes massive labradorite so appealing is the play of colors caused by its internal structure. As this feldspar crystallizes, it has a penchant for forming what is called polysynthetic twinning or lamellar twinning. This is referred to as a two-phase razor-thin intergrowth of sodium and calcium feldspar, which alternate such that their structure interferes with and scatters light entering the stone. These alternating microstructures form a regular pattern of closely spaced parallel lamellae that vary slightly in chemical composition, acting like a diffraction grating scattering light that splits into its component colors. Some colors are absorbed, but others are reflected for the viewer to see and enjoy.
This colorful display is often called labradorescence. The surface of the stone flashes broad to narrow bands of color, sometimes soft and iridescent, and sometimes bright and flashy. As you rotate the stone, it changes the angle at which the light strikes the piece making the colors wax and wane and change hues.
In Labrador, the native people initially called the stone “fire rock”. Depending on the pattern of colors seen in the rock, it has been called bull’s eye, lynx eye, opaline feldspar, ox-eye and the aforementioned spectrolite. In gem form it is called sunstone.
Collecting labradorite is certainly possible. There are a number of outcrops of this rock widespread throughout the Adirondack Mountains in northern New York State. I was able to collect big chunks of colorful stone years ago when I was driving to Montreal on a newly opened section of Interstate 87. Several feldspar outcrops along this highway flashed colors at me as I drove along. Collecting was simply a matter of picking up loose chunks. Local rock hounds can collect colorful labradorite if they take the time to look in several counties in northern New York State where labradorite occurs.
RUSSIA’S LAY TO CLAIM
The most remarkable use of labradorite I have seen was in Russia. Large carvings of the stone were displayed in several museums.
Most impressive was its use as a decorative stone in the Kremlin. Inside the Kremlin walls are well-manicured vast grounds. Here and there are huge flower beds, each measuring perhaps ten meters on one side. These flower beds are bordered by large stone blocks of a variety of handsome stone. As we walked along the Kremlin grounds, one of these rock borders flashed colorfully in the sunlight. It was made of choice labradorite flashing blue, bronze, red and golden in the sunlight. Each block was about 20 centimeters thick, perhaps a meter long and a half meter above the ground. The play of colors in the stones was exceptional. Unfortunately, inside the Kremlin at that time we were not allowed to use cameras. I later found out the source of this wonderful labradorite was Galovinskoe, Volyhn district, Russia. Other huge deposits of labradorite in Russia are found at Kiev, Ukraine and Dzhugdzhur. Like so many lapidary gemstone deposits in Russia, especially in Siberia, deposits of additional gem materials like rhodonite, jasper, charoite and jade are prevalent. Only poor transportation prevents them being brought to market in quantity.
In its lovely crystalline gem form, labradorite exhibits a variety of colors, especially the sunstone from Oregon. The common color in these gems is yellow, but when micro-crystals of copper are included, the color can be red, green, and occasionally violet. Such gem material occurs as phenocrysts in basalt or similar volcanic rock. These deposits are not rare though most are limited in scope and are generally claimed.
South Central Oregon has large deposits of gemmy labradorite south of the town of Plush and near Burns in Harney County, Oregon.
Heavy equipment is used to move the near-surface weathered volcanic rock, which is broken up, to release phenocrysts of gemmy feldspar. Sorted by size and quality, the better pieces are faceted and offered for sale. Because of the relative abundance of gem labradorite in some areas of Oregon, the gem was named Oregon State’s official gemstone in 1987.
Rockhounds interested in collecting gem labradorite sunstone in Oregon have both fee digging and public land opportunities to dig for this pretty gem. There are fee dig mines listed on the internet. Sites can open or close with little warning so check carefully.
There are also public lands that can be accessed. Use the internet and go directly to the BLM Lakeview District Lakeview Resource Area, Oregon. This website has information on sunstone possibilities. There are nearly 8,000 sunstone claims filed at this time, but only a few are open to fee digging. That information can be obtained from the internet and the BLM office in the Lakeview area. According to the latest BLM listing, 97 percent of the filed claims are closed.
If you wish to dig on available public lands you have to contact the Lakeview office for the most current information. The internet site lists their phone number and address.
MINING IN MEXICO
Another great sunstone locality is an area in Mexico that Carol and I visited as noted dealers Benny and Elva Fenn’s guests. They had discovered this deposit accidentally while following the trail of a coyote they had trapped. The animal had broken loose and was found on a gem site, where Elva began picking up yellow gemmy crystals scattered on the slopes of a weathered volcanic flow. Careful examination and later testing proved these gemmy phenocrysts were labradorite as they are a calcium-sodium feldspar with a close to 50-50 mix of the two metals. If you see this yellow gem being offered for sale at shows and on the internet now you know the story of how it came to be discovered.
During our visit, we also toured the Fenn’s gem mining operation. The lava flow, some twenty feet thick,
was topped by a later lava flow of different texture and composition that prevented the earlier flow from cooling too rapidly. This slow cooling allowed the molecules of labradorite to develop into phenocrysts and grow to exceptional size, with some showing crystal faces and terminations.
Mining the labradorite gem rough was simple. They used a front loader to scoop up the weathered and broken lava, dumping it onto a shaker table where workers handpicked the gemmy fragments allowing the waste to fall off the sloping table. The larger crystalline pieces often show crystal faces, and in some cases, terminations, indicating they had partially crystallized within the lava before it had hardened. The recovered gems, after careful hand-selecting, were bagged and shipped out of Mexico to Southeast Asia for faceting and marketing.
We took the opportunity to collect many of the larger pieces that were gemmy and suited for faceting. We filled two large plastic bags in a matter of an hour. Later I had several self-collected labradorite gems faceted for the ladies in my family. The gems were wire wrapped as pendants, a suitable setting for a gem that has a hardness of six!
ADDITIONAL LABRADORITE DESTINATIONS
While the deposit in Mexico is no longer being worked, good colorful labradorite has been found within the United States, including areas in the Ouchita Mountains of Arkansas, San Gabriel Mountains near Los Angeles, and the San Marcos mountains nears San Diego, among other places. In Arizona there is a huge volcanic area that yields massive pieces of gem labradorite. South of the mining town of Ajo, on the road to Guaymas, Mexico, travelers pass through a huge volcanic area known as the Pinacote volcanic field. As you walk over this vast area of black volcanic rock, labradorite crystal fragmentscan be found. For the curious who live in or near New York City, you might check the façade of the Chrysler building, one of the city’s landmarks, because the facade is made with very fine labradorite.
For a very common feldspar mineral, labradorite is one of the more interesting minerals and rocks for the working lapidary. Being able to dig large colorful masses to cut and polish or collect small delicately colored gems for faceting on your own is rockhounding at its best!