There are two completely different minerals associated with the name "jade," "nephrite," and "jadeite." Jadeite is a pyroxene, part of a rock-forming silicate mineral group associated with metamorphic rock, while nephrite is an amphibole, a variety of actinolite that is part of the rock-forming inosilicate mineral containing ions of iron and/or magnesium. The mineral Jadeite is comprised of blocky, interlocking granular crystals, while nephrite is comprised of fibrous crystals. These differences are what accounts for the identifiable characteristics of each mineral. Jadite is described as having a granular, or "sugary" texture, whereas nephrite's texture is described as "silky."
Jadeite
Jadeite is white in its pure state, but does occur in a wide range of colors due to trace impurities. Dark green jadeite is colored by the presence of iron, emerald-green jadeite (Imperial Jade) is colored by chromium, and lilac jadeite is colored by manganese. Pink, brown, orange, red and even black or "Olmec blue" jadeite obtains its color from inclusions of foreign minerals.
Pink Jade Bracelet by Michael Zobel (left) - White Jade Earring by Jeff & Susan Wise (right)
Jadeite is typically found as boulders or small pebbles in alluvial deposits located near subduction zones (California, Japan). Myanmar (Burma) is a significant source for "Imperial Jade." Weathered jadeite typically has an "orange peel" like texture that is sometimes utilized in the final texture of carvings.
Nephrite
Nephrite occurs in a very limited color range of Pale green to dark green. Nephrite is whitish-gray when actinolite asbestos is present.
In New Zealand, nephrite jade (aka greenstone) was worked for centuries by Maori to fashion ornaments and weaponry, and is still widely used to make carved jewelry. The Maori word for "greenstone" is pounamu.
Nephrite was the only form of jade used in Europe until the 16th century when Spanish explorers brought jadeite back from Mexico. The Spaniards referred to this material as piedra de ijada or "stone of the loins" which was mistranslated into the French pierre de jade, the origin of the word "jade."
Maw-Sit-Sit
The towns of Hpakan and Tawmaw are the main jade mining regions in North-Western Myanmar (Burma). Jade from this region is transported down the Ayeyarwady or Irrawaddy River, from the port city of Myitkyina - a major trading hub for both jade and opium.
Maw-sit-sit is a rare, intense green variety of jadeite found in Tawmaw. First discovered in 1963, maw-sit-sit is composed of jadeite and chromite with chromium (Cr) as the principle coloring agent, and kosmochlor (Ko) forming the black spots.
Jade in China
Jade was considered a royal gem in China from the earliest dynasties up until present, and is a major part of the ancient (and modern) Chinese culture. Most of the "jade" used in China prior to the 17th and 18th centuries was nephrite. The largest nephrite jade deposits in China were in the region of Khotan in the Western Chinese province of Xinjiang.
More on: Chinese Imperial Jade
Jade in Other Cultures
In Pre-Columbian times (1200 BC - 400 BC), Jadeite was fashioned by the Olmec, people of Mayan decent, living in the region of what is now Veracruz and Tabasco, Mexico. The dark blue-green jadeite variety that the Olmec used is now known as "Olmec Blue" jade, and is still being used today by the indigenous peoples of Guatemalan.
Physical Properties of Jadeite
Jadeite crystallizes in the monoclinic crystal system with a fibrous, granular or massive crystal habit.
Jadeite has a hardness of 6.5 to 7 on the Mohs scale, a specific gravity of 3.25 to 3.35, and a refractive index of 1.665. Jadeite has a vitreous luster.
Jadeite Chemical Composition: NaAlSi2O6
Physical Properties of Nephrite
Nephrite is an aggregate variety of actinolite (asbestos) which crystallize in both the monoclinic and orthorhombic triclinic crystal system. Nephrite is a softer material with a hardness of 5 to 5.6 on the Mohs scale, and a refractive index of 1.610. Nephrite has a vitreous to dull glassy luster, and can exhibit some pleochroism.
Nephrite Chemical Composition: Ca2(Mg, Fe)5Si8O22(OH)2
Physical Properties of Maw-Sit-Sit
Maw-Sit-Sit is a translucent to opaque metamorphic rock composed of spheroidal or ellipsoidal aggregates of chromian jadeite, symplektite, ureyite and kosmochlor (Ko). Maw-Sit-Sit has a similar hardness to jadeite, 6.5 to 7 on the Mohs scale, a specific gravity of 2.50 to 3.50, and a refractive index of 1.52. Maw-Sit-Sit has a vitreous luster.
Jadeite Chemical Composition: NaCrSi2O6
Semi-Precious Stones