Jade is revered across cultures for its toughness, color, and symbolic weight. The term refers to two distinct mineral species: jadeite and nephrite. While they share a similar appearance and cultural significance, they differ fundamentally in chemical composition and geological origins. Understanding how this prized stone is formed requires exploring the forces of plate tectonics and the craft of human artisans.
The Creation of Jadeite
Jadeite, the rarer and often more valuable form of jade, is a sodium aluminum silicate requiring extreme geological conditions to form. Its creation is linked to the dynamics of plate tectonics, specifically in active subduction zones where one plate is forced beneath another.
This process subjects sodium-rich rock materials deep within the Earth to pressure exceeding 10,000 atmospheres while maintaining a relatively low temperature. This high-pressure, low-temperature metamorphism encourages the crystallization of jadeite from precursor minerals in the presence of water-rich fluids.
Over millions of years, tectonic activity gradually uplifts the jadeite deposits closer to the surface, making them accessible for mining. The highest quality jadeite, often called Imperial Jade, owes its intense emerald-green color to trace amounts of chromium. Significant commercial deposits are rare, with Myanmar (Burma) being the most historically important source.
The Creation of Nephrite
Nephrite, the more common form of jade, is a calcium, magnesium, and iron-rich silicate belonging to the amphibole mineral group. Its formation is a metamorphic process occurring under less extreme geological conditions than jadeite, typically through metasomatism where hot fluids interact with magnesium-rich rocks.
This transformation occurs at the contact zones between serpentine or dolomite rock and other silica-saturated rock types. Water-rich fluids react with the parent rock, resulting in the formation of the fibrous, tightly intergrown crystals of the tremolite-actinolite series that define nephrite. Nephrite ranges in color from creamy white, known as “mutton fat jade,” to various shades of green.
The fibrous structure gives nephrite exceptional toughness, making it highly resistant to breakage, though its hardness is slightly lower than jadeite. Nephrite is found globally, including in Canada, Siberia, and the Kunlun Mountains of China, tied to these specific contact metamorphic environments.
Shaping the Stone: Processing Raw Jade
Once extracted, the raw jade must be transformed into a polished object. Both nephrite and jadeite challenge artisans due to their exceptional toughness, resulting from their tightly interlocked microcrystalline structure. Cutting and shaping the stone is accomplished through abrasion rather than chiseling.
Modern processing relies heavily on diamond-tipped tools, as diamond is the only material hard enough to efficiently cut jade. Initial shaping is done using diamond-coated saw blades or wire saws for precise cuts. Water is continuously used to lubricate and cool the stone and the tools.
After the primary shape is established, the stone moves through grinding and sanding using progressively finer abrasive grits. Diamond burrs and grinding wheels carve intricate details and smooth the surface. The final stage involves polishing the jade with extremely fine abrasive compounds, such as diamond powder or tin oxide, to bring out the stone’s natural luster.
Understanding Jade Treatments and Enhancements
In the commercial market, jade is categorized by the extent of treatment it has received, which impacts its value and durability. Enhancements are applied to lower-quality jadeite rough to improve color or translucency. The industry uses a classification system to denote the level of alteration.
Type A jade is completely natural, having only undergone traditional cutting and polishing. This untreated material retains its original internal structure and color, making it the most valuable.
Type B jade is chemically treated, typically soaked in strong acid to remove impurities, which weakens the stone’s crystalline structure. The resulting voids are filled with a polymer resin to enhance transparency and stability. This treatment makes the stone less durable over time as the polymer can degrade.
Type C jade is material that has been dyed to introduce or enhance color. This dyeing often occurs after the acid and polymer treatment (Type B+C).