Jade is a gemstone revered across diverse cultures for its beauty, durability, and deep symbolic meaning. For thousands of years, this material has been treasured, particularly in East Asia, where it symbolizes virtue, purity, and immortality. Ancient Chinese artisans carved it into ritual objects and ceremonial vessels, calling it the “Stone of Heaven” (yù). Mesoamerican civilizations, notably the Olmec and Maya, also prized the stone, reserving its use for the highest echelons of society and powerful rulers.
The Dual Identity of Jade
The term “jade” refers to two distinct mineral species: Jadeite and Nephrite. Although both minerals look similar and have been used interchangeably throughout history, they possess different chemical compositions and crystal structures. Geologically, they form under contrasting metamorphic conditions, resulting in unique physical properties. The scientific distinction between the two was not formally recognized until 1863, long after both materials had become culturally established as “jade.”
Jadeite: The Pyroxene Gem
Jadeite is classified as a pyroxene mineral, characterized chemically as a sodium aluminum silicate, with the formula NaAlSi2O6. This mineral has a compact, granular crystal structure, which contributes to its vitreous luster when polished. It is the harder of the two jades, rating between 6.5 and 7 on the Mohs scale, and is also denser, with a specific gravity ranging from 3.24 to 3.43.
The colors found in Jadeite are more varied than in its counterpart, including white, red, black, blue, and lilac or lavender. The most sought-after variety is “Imperial Jade,” which exhibits an intense, translucent emerald-green hue caused by trace amounts of chromium. Jadeite forms exclusively under high-pressure and relatively low-temperature metamorphic conditions, typically found within subduction zones. The world’s most significant and commercially important source of gem-quality Jadeite is found in Myanmar, historically known as Burma.
Nephrite: The Amphibole Gem
Nephrite is an amphibole mineral belonging to the tremolite-actinolite series, possessing a complex chemical formula of Ca2(Mg, Fe)5Si8O22(OH)2. Its internal structure is a dense, microscopic aggregate of interlocking, fibrous crystals, unlike the granular structure of Jadeite. This fibrous matrix makes Nephrite exceptionally tough and resistant to breaking, with a hardness falling between 6 and 6.5 on the Mohs scale.
The appearance of Nephrite is characterized by a softer, waxy or oily luster, which differs from the glassy look of Jadeite. Its color palette is limited to shades of white, cream, dark green, gray, and black. The highly valued white Nephrite, historically mined in China, is known as “mutton fat jade,” while dark, iron-rich varieties are called “spinach jade.” Nephrite forms in regional metamorphic environments, often associated with serpentine rock deposits in areas like New Zealand and Western Canada.
Identifying and Assessing Quality
Distinguishing between Jadeite and Nephrite involves comparing their physical properties, specifically density and luster. Jadeite, being denser, will feel heavier than Nephrite of the same size, a difference that is sometimes noticeable by simply holding the stones. The surface appearance is also a clue, as polished Jadeite displays a bright, vitreous sheen, while Nephrite exhibits a duller, more resinous, or waxy luster.
On the market, the value of jade is determined by a combination of color saturation, purity, and transparency, with high-quality Jadeite commanding the highest prices. The most valuable pieces are the intensely colored, highly translucent Imperial Jade, which can be valued significantly higher than the finest Nephrite.
The industry uses a classification system for treated jade to ensure transparency for buyers.
- Type A jade is defined as natural, untreated material, with only traditional processes like waxing permitted to enhance the surface.
- Type B jade has been chemically treated with acid to remove impurities and then infused with a polymer resin to improve its appearance and translucency.
- Type C jade has been artificially dyed to introduce or enhance color.
Both Type B and C treatments compromise the stone’s integrity and durability, causing a dramatic reduction in market value compared to natural Type A jade.