Jade is an ornamental stone. The term jade jewelry is applied to two different metamorphic rocks that are made up of different silicate minerals which is actually two different stones, Jadeite and Nephrite.
Jade is derived from the Spanish ‘piedra de ijada’, loin-stone, jade having been recognised by the Amerindians as a remedy for kidney ailments. Because of its beneficial effect on the kidneys, the stone was also known as ‘lapis nephriticus’. That, indeed, is where the term ‘nephrite’ came from.
Nephrite jade, consists of a microcrystaline interlocking fibrous matrix of the calcium, magnesium-iron rich amphibole mineral series tremolite (calcium-magnesium)-ferroactinolite。Nephrite’s robustness is due to the fact it contains tremolite. It also can be divided into several sub-classifications according to color: white, grey, green, topaz, and black jade.
Chemistry: Ca2(Mg,Fe)5(OH)2(Si4O11)2 , avariety of actinolite.
Index Of Refraction: 1.62 (nephrite)
Hardness: 6.5 – 7
Cleavage: n/a-massive stone
Crystal System: monoclinic
Pure Nephrite is white. Nephrite is usually green or creamy white, but can also be beige, yellow, blue or black and often contains veins of color. The presence of iron provides the green in nephrite.
Nephrite’s uses include jewelry, carvings and bowls and vases. Because of its toughness, ancient cultures used it to make symbolic ornaments, axes, knives and weapons.
When Jade is sold under names such as New Jade, Korean Jade, Stygian Jade, Pagoda stone, Mexican Jade, and Indian Jade, it is most often fake. Jewelers may also dye poor quality jade to enhance the color.
Jadeite jade, a rock consisting almost entirely of jadeite, a sodium- and aluminium-rich pyroxene. The gem form of the mineral is a microcrystaline interlocking crystal matrix.
Chemistry: NaAlSi2O6 , Sodium Aluminum Silicate
Transparency: Examples are generally opaque to translucent
Crystal System: monoclinic; 2/m
Cleavage: is poor in two directions at near 90 degree angles, but is never seen in massive specimens
Fracture: Splintery to Uneven
Hardness: 6.5 – 7 (extremely tough, actually stronger than steel)
Specific Gravity: approximately 3.3 – 3.5 (above average for translucent minerals)
Flame Test: Sodium result-yellow
Best Field Indicators: Toughness, green color, density, flame test and hardness
Index Of Refraction: approximately 1.66
Jadeite Chemical Composition
Jadeite is the very rare chemical combination, NaAlSi2O6, Sodium Aluminum Silicate, which is very close to the very common minerals, Albite, NaAlSi3O8, and Nepheline, NaAlSiO4. However, because of the extreme force under which Jadeite forms, its specific gravity (3.3-3.5) is much higher than that of Albite (2.61) or Nepheline (2.60 – 2.65).
Jadeite Geological Environment
Jadeite is rarely found in its original geological environment; most specimens are found in river gravels and boulders. It forms in zones that have experienced the extreme forces of continent to continent contact. In theses collisions, Albite loses a SiO2 molecule to form a Quartz and Jadeite.
Jadeite Crystal Structure/habit
Most Jadeite occurs as very tough massive specimens of tightly interlocked crystals in; crystals of the mineral are rare but exhibit the Monoclinic system of three axes of unequal lengths, two perpendicular to each other while the third intersects the plane of the other two at an angle inclined to one of them and at a 90 degree angle to the last one. Jadeite does occur as granules in metamorphic rocks.
Although famous for its green, pure jade is actually white, with impurities forming green, red, yellow, pink, white, violet, orange, blue-green and brown. Jadeite is usually more vivid in color than Nephrite. Jadeite is the only one of the two that produces the highly prized emerald green Jade called Imperial Jade. Jadeite gets this emerald color from chromium. Other colors are also formed from impurities. Brown indicates the presence of iron and Violet, manganese.
Both of jadeite and nephrite are tough, since they consist of dense, close-grained, matted aggregates, but they differ from one another in their chemical composition and colours. Nephrite ranges mainly from mid to dark green or grey-green, but it can also be white, yellowish or reddish. Rarer, and somewhat tougher, jadeite displays hues which include green, but also white or pink, and reds, blacks, browns and violets. In both minerals, the way the colour is distributed varies a great deal. Only in the very finest jade is the colour evenly distributed. Both nephrite and jadeite often have veins, blemishes and streaks running through them, though these may not always be regarded as flaws. On the contrary, some of these patterns are considered particularly valuable.