Jadeite is a pyroxene mineral with composition NaAlSi<sub>2</sub>O<sub>6</sub>. It is hard (Mohs hardness of about 6.5 to 7.0), very tough, and dense, with a specific gravity of about 3.4. It is found in a wide range of colors, but is most often found in shades of green or white. Jadeite is formed only in the subduction zones of continental margins, where rock undergoes metamorphism at high pressure but relatively low temperature.
Jadeite is the principal mineral making up the most valuable form of jade, a precious stone particularly prized in China. Most gem-quality jadeite jade comes from northern Myanmar. Jade tools and implements have been found at Stone Age sites, showing that the mineral has been prized by humans since before the beginning of written history.
Name
The name jadeite is derived (via and ) from the Spanish phrase "piedra de ijada" which means "stone of the side". The Latin version of the name, lapis nephriticus, is the origin of the term nephrite, which is a different mineral that also shares the common name jade.
Properties
Jadeite is a hard, extremely tough, rare mineral of the clinopyroxene family of minerals.
Though highly variable in color, it is typically apple-green to emerald-green, or less commonly white or white with spots of green.
Jadeite has a Mohs hardness of 6.5 to 7, slightly less than that of common quartz.
Jadeitite is resistant to weathering, and alluvial boulders of jadeitite released from the serpentine-rich environments in which they formed can have weights of up to tons. Raw specimens having Burmese tax stamps or polished slots for evaluating quality are prized by some collectors. Color is largely affected by the presence of trace elements such as chromium and iron. Its translucence varies from opaque to almost clear. It is found exclusively in high-pressure, low-temperature metamorphic rock of continental margins. California, and Guatemala.
In the 1980s, General Electric and other research groups produced synthetic jadeite in controlled settings for materials science and petrological research. However, despite such experimentation, commercial-scale production has not occurred due to the difficulty and costs associated with synthetic production. The pressure and temperature requirements are expensive and, as such, mining remains more cost effective.
Uses
Jadeite is the dominant mineral of the most desirable variety of jade. Jadeite jade is the most valuable form, Jadeite jade first came into significant use in China only towards the end of the 18th century, as fei tsui.
Jadeite from the Motagua Valley, Guatemala, was used by the Olmec and Maya peoples, as well as the indigenous peoples of Costa Rica.
Unusual colors, like "Olmec blue" jade, which is characterized by its deep blue-green, translucent hue with white flecking, are becoming more highly valued because of its unique beauty and historical use by the Mesoamerican Olmec and also in Costa Rica.
Stone Age use
thumb|Polished [[Neolithic jadeitite axe-head from the Museum of Toulouse]]
Over 180 axe heads made from jadeitite quarried in northern Italy in the Neolithic era have been found across the British Isles. Because of the difficulty of working this material, all the axe heads of this type found are thought to have been non-utilitarian and to have represented some form of currency or be the products of gift exchange.
A great many jadeite beads and axe heads as well as the remains of jadeite workshops from the Neolithic era have been uncovered in Itoigawa, Japan. These beads and axes were traded throughout Japan and the Korean Peninsula and were produced by the world's oldest known jadeite-using culture, centered on the Itoigawa region.
thumb|[[Maya civilization|Maya Jadeite Plaque, 600–900 AD, Brooklyn Museum|upright]]
See also
- Clinopyroxene thermobarometry
- Costa Rican jade tradition
- Jade use in Mesoamerica
- List of minerals