Jadeite
CatgorieIX: silicates | |
|---|---|
 | |
| Empirical formula | NaAlSi 2 O 6 or Na (Al, Fe 3 +) Si 2 O 6 |
| Color | Variable, often varying shades of green. |
| Crystal class and space group | Prismatic 2 / m C2 / c |
| Crystal system | monoclinic |
| Bravais lattice | C centered |
| Cleavage | {110} good |
| Fracture | irregular, splintery |
| Brightness | glassy subvitreux |
| Polished shine | fatty |
| Trait | White |
| Transparency | Opaque to translucent |
| Density | measured: 3.24 to 3.43 calculated: 3.33 |
Jadeite is a mineral family of silicates , class inosilicates , group of pyroxenes whose chemical composition is ideal Na Al If 2O 6. The mineral is typical of a metamorphic high pressure and low temperature.
It is the rarest of the two minerals covering the name jade , the other is nephrite.
Summary |
Inventor and etymology
Alexis Damour describes and names the jadeite in 1863 .
The names jade, jadeite and nephrite have the same origin: lapis nephriticus is the Latin equivalent of the Spanish piedra de ijada, that is to say the stone side, referring to its use by the peoples of Mesoamerica for curing various internal ailments, including problems nephritis .
Appearance, physical properties
Jadeite crystallizes only rarely in small crystals prismatic well trained. It is found most often in the form of aggregates or micro finely granular , or masses cryptocrystalline with a compact structure sometimes fibrous.
The mineral density (3.24 to 3.43) and hard (6 to 7 on the Mohs scale ). It is very tenacious , especially in its compact form. The fracture is irregular and splintery. The cleavage is good {110}.
Jadeite is allochromatic: pure, it is theoretically clear, colorless. In fact it is translucent, white or pale gray, because of impurities and defects in the crystal lattice. Jadeite of great purity is rare. Generally it is almost opaque and colored by some transition metals present in trace amounts: Iron mainly Titanium , Chromium , Manganese ... The most common color is Green, from the lightest to darkest. More rarely, other colors are available: green-blue, blue, pink, purple, purple, brown-orange ... Its luster is vitreous or subvitreux, slightly pearly, when the structure is fibrous, pearly on cleavage, fat on the polished faces. Its trace is white.
Crystal chemistry
Jadeite is a silicate of the class inosilicates , group of clinopyroxene. Its structure is a blend of simple infinite chains whose pattern is a combination of two groups tetrahedral Crystallography
The structure of jadeite, similar to that of diopside , characteristic of pyroxene , is known since the work of Prewitt and Burnham in 1966 .
It belongs to the family crystalline monoclinic , the crystal class prismatic (holodrie) 2 / m and the space group C2 / c. Chain Pattern Gallery
Ax Neolithic jadeite - Colomiers - Museum of Toulouse 
Untransformed block of jadeite and jadeite statuette polished
Mask jadeite Olmec 
Jadeite antique buttons made by hand (China)
 | Click on a thumbnail to enlarge |
References
Bibliography
Articles and books cited:
- Alexis Damour, "Notice and analysis on the jade green. Meeting of this mineral to the family Wernerites, "in Proceedings of the weekly meetings of the Academy of Sciences, Vol. 56, 1863, p. 861-865 Notes
Related articles
External Links
- Structure of jadeite in 3D webmineral.com
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