Alaskan jade is one of many types of green rock bearing the sometimes misleading title of jade. As a gemstone, jade is broadly separated into two distinct classes: jadeite, which is the Chinese form of jade, and nephrite jade, into which class Alaskan jade falls. Nephrite jade is composed of minerals in the amphibole group, while jadeite is made up of minerals in the pyroxene group. The groups have different compositions.
Jade is a term applied by gemologists to describe certain types of metamorphic rock not because of a specific mineralogical composition, since two entirely different types of jade exist, but because of the texture of the rock itself.
A gem’s hardness rating is based on the Mohs Scale, a standard used by the gem industry. Friedrich Mohs (1773-1839), was a German geologist and mineralogist who developed a mineral classification database using physical characteristics rather than chemical composition. The higher the Mohs Scale number, the harder the gemstone. Diamonds are rated as a 10 on the Mohs Scale, which is the highest rating. Jadeite, or Chinese jade, is Mohs Scale 7. Gemstones with less than a 7 rating are easily scratched.
Alaskan jade is made of pectolite and is a nephrite jade. Nephrite jade has a hardness rating of 4.5 to 6.5. This softer jade is easier to carve, and most of the less expensive carved jade pieces nowadays are nephrite jade.
Green Chinese jade is usually lighter than Alaskan jade. Jadeite, or Chinese jade, comes in a variety of colors, however, including red, yellow, green, white, pink, blue, brown, black, orange and lilac. The more common nephrite jade of the Alaskan variety is found in many shades of green. Alaskan jade used in jewelry making is usually a rich, dark green.
Chinese jade is mined in southern China, upper Burma and Tibet.
Large deposits of Alaskan jade are found along the Seward Peninsula, particularly in Jade Creek and Jade Mountain in northwestern Alaska. Alaskan jade may also be found in parts of California and in British Columbia. In fact, although Alaskan jade is Alaska’s state gem, British Columbia supplies most of the world’s nephrite jade.
Nephrite jade is made up of various mineral species in the amphibole group. Alaskan jade is only one of several types of this softer jade gemstone found worldwide.
Jadeite jade’s mineral aggregates come from the pyroxene group.
Chemically, both groups are inosilicates or chain silicates, but each has different mineral compositions and molecular structures.
Only an expert in jade has a chance of identifying the difference between Alaskan jade and Chinese jade just by looking at it. Obtaining a definitive identification of either jade type requires a microscope, spectrograph and scientific tests.
The amateur may try looking at the subtle variations in both the gem’s sheen and surface texture to differentiate between Chinese jade and Alaskan jade, or try scratching it with a sharp instrument, and make an “educated guess.” It is best to consult a professional jeweler for an expert opinion.
References and ResourcesU.S. Department of the Interior Bureau of Land Management: "Hidden Treasures"