Semi-Precious Gemstones: Jade, Jadeite, Nephrite, Maw-Sit-Sit
Jade used in Jewelry
Source: Burma (Myanmar), China, Coastal California (USA), Mexico, New Zealand
There are two completely different minerals associated with the name "jade" which are nephrite and jadeite. Jadeite is a pyroxene which is 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 minerals containing ions of iron and/or magnesium.
The mineral jadeite is comprised of blocky, interlocking granular pyroxene crystals that are described as "feathery," while nephrite is an aggregate comprised of densely-packed 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." A gem-quality specimen of jade must no only have a rich hue, but must also have good diaphaneity, or translucency.
Jadeite
Jadeite is white (colorless) in its pure state, but does occur in a wide range of allochromatic 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.
Lilac jade (jadeite) bracelet by Michael Zobel |
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White jade, opal & black onyx earrings |
Jadeite is typically found as boulders or small pebbles in alluvial deposits located near subduction zones (California, Japan). Weathered jadeite typically has an "orange peel" like texture that is sometimes utilized in the final texture of jade carvings. Myanmar (Burma) is a significant source for "Chinese Imperial Jade" which is a highly prized variety of jadeite.
Jadeite Chemistry, Physical Properties
Nephrite
Nephrite occurs in a very limited color range of pale green to dark green hues. Nephrite is whitish-gray when actinolite asbestos is present in the mineral. Nephrite is an aggregate variety of actinolite (asbestos) which crystallize in both the monoclinic and orthorhombic crystal system.
In New Zealand, nephrite jade (aka greenstone) was worked for centuries by Maori tribesmen 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."
Nephrite Chemistry, Physical Properties
Mawsitsit
Maw-sit-sit (Mawsitsit) is a rare, intense green variety of jadeite found in Burma. First discovered in 1963, maw-sit-sit is a translucent to opaque metamorphic rock composed of spheroidal or ellipsoidal aggregates of chromian jadeite (jadeite and chromite), symplektite, ureyite and kosmochlor (Ko). The principle coloring agent of maw-sit-sit is chromium (Cr), with kosmochlor (Ko) forming the black spots.
The towns of Hpakan and Tawmaw are the main Mawsitsit jade mining regions in north-central Myanmar's (Burma's) Kyaukseinmyo ("Jade Land") region. 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. Mawsitsit from Kyaukseinmyo also finds its way into the gem-trading city of Mae Sot in north-western Thailand.
Maw-Sit-Sit Chemistry, Physical Properties
Cultural Significance of Jade
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.
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.
More on: Chinese Imperial Jade
Bibliography and Reference on Jade & Jadeite
1. T. Miyazoe, Coexistence of pyroxenes jadeite & diopside  . www.geoscienceworld.org
2. Joe Smyth, Pyroxene Group . www.ruby.colorado.edu
3. Thomson Gale, Shock Metamorphism & Jadite . www.accessmylibrary.com
4. G.M. Bancroft, The Diopside-hedenbergite series . www.minsocam.org
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