Jade, that beautiful and coveted mineral that presents numerous colors from white and yellow to varied greens, is a stone used in China and Burma for centuries for carving daggers and knives, and in jewelry.
Found in many parts of the world from the Americas to China, it is formed in areas that have “subduction” zones. To understand “subduction” you have to understand plate tectonics.
Plate tectonics is a theory that the Earth’s surface is made from a series of plates, which float on the Earth's liquid mantle. It explains many natural phenomena such as volcano clusters, earthquake producing faults (or cracks in the surface of the Earth), and the locations and height of many mountain ranges.
Because these tectonic plates float, they also move and occasionally collide with one another, and this is where “subduction” zones are created as one tectonic plate slides beneath another plate. “Subduction” occurs when two tectonic plates collide, and one ends up under the other. The lower plate will take the stone to depths where the necessary intense pressure, heat and minerals will eventually form it into jade. A high pressure, low temperature metamorphic environment is necessary to form the stone known as nephrite or jadeite.
The composition and structure of these two jade varieties are quite different. Nephrite is composed mostly of interwoven mineral fibers, while jadeite is composed of interlocking granules.
Nephrite is also a form of actinolite, which is composed of minerals like sodium, calcium, titanium, manganese, magnesium, iron, silicon, aluminum, hydrogen and oxygen, along with water. Its surface tends to look oily and smooth with little pitting. It is often found in California, British Columbia, Taiwan, Russia, Alaska and in New Zealand. Its hardness on the Mohs scale is about 5.5 to 6. The Mohs scale measures the hardness of stones on a scale from one to ten.
Jadeite, rarer than nephrite, is a much simpler mineral made of aluminum, pyroxene, chromium, sodium, iron, oxygen and silicon. About forty-five percent of each of these jades are composed of oxygen. It is chromium that gives jadeite its deep rich green coloring. It is about a 6.5 to 7 on the Mohs scale, which makes it closer to quartz. It is found in fewer locations worldwide, usually in places around Burma and Guatemala.
There actually is a third type of jade known as chloramelanite, which is a variety of jadeite. It is mostly dark green or black and is hardly attractive enough to use in carvings and jewelry. Still, people may prefer this variety because it is different.
Jade is one of Mother Nature’s toughest minerals, next to the black diamond. Although it is often carved, it is practically indestructible. Formed from mountain and water, it is symbolic of the Earth. Jade comes in colors that include gray, pink, white, yellow, orange and beautiful greens.
In ancient China, nephrite jade was used mostly in carvings, while new jade or jadeite, was introduced from Burma in the 1780’s. The brilliant deep green jade in much jewelry today is known as imperial jade.
There are several colors and formations of jade. Chrome jade has brilliant green speckles within the stone, while chatoyant jade has a tiger-eye effect. Botryoidal jade, or bubble jade, is shaped like little clumps of grapes. Vulcan jade from California will appear with a golden brown coloring.
The stone is mined in large blocks or boulders. In the Pacific Northwest, it can be exposed by the action of earthquakes, land movement and water. In Washington State, people have occasionally found jade above the ground.