Jadeite
| Jadeite | |
|---|---|
Jadeite from Burma
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| General | |
| Category | Pyroxene group |
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Formula (repeating unit) |
NaAlSi2O6 or Na(Al,Fe3+)Si2O6 |
| Strunz classification | 9.DA.25 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | C2/c |
| Identification | |
| Color | Apple-green, emerald-green, bluish green, leek-green,greenish white, white, may show green spots, rarely blue or violet; colorless in thin section. Often also banded. |
| Crystal habit | Commonly massive, or fibrous, granular; prismatic crystals rare |
| Twinning | Single and lamellar twinning on [100] and [001] |
| Cleavage | Good on [110] |
| Fracture | Splintery |
| Mohs scale hardness | 6.5 - 7 |
| Luster | Subvitreous, pearly on cleavages |
| Streak | White |
| Diaphaneity | Translucent |
| Specific gravity | 3.24 to 3.43 |
| Polish luster | vitreous to greasy |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 1.654 - 1.673 nβ = 1.659 - 1.679 nγ = 1.667 - 1.693 |
| Birefringence | δ = 0.013 - 0.020 |
| Dispersion | r > v; moderate to strong. |
| Ultraviolet fluorescence | Dark colors are generally inert. Light green – inert to weak white in long wave, generally inert in short wave; light yellow – inert to weak green in long wave, generally inert in short wave; white – inert to weak in long wave, generally inert in short wave; light purple – inert to weak white or weak brownish red in long wave, generally inert in short wave; some dyed lavender colors – moderate to strong orange in long wave, weaker in short wave |
| References | |
Jadeite is a pyroxene mineral with composition NaAlSi2O6. It is monoclinic. It has a Mohs hardness of about 6.5 to 7.0 depending on the composition. The mineral is dense, with a specific gravity of about 3.4.
The name jadeite is derived (via French: l'ejade and Latin: ilia) from the Spanish phrase "piedra de ijada" which means "stone of the side". It was believed to cure kidney stones if it was rubbed against the side of the afflicted person's body. The Latin version of the name, lapis nephriticus, is the origin of the term nephrite, which is also a variety of jade.
Jadeite forms solid solutions with other pyroxene endmembers such as augite and diopside (CaMg-rich endmembers), aegirine (NaFe endmember), and kosmochlor (NaCr endmember). Pyroxenes rich in both the jadeite and augite endmembers are known as omphacite. Jadeite is formed in metamorphic rocks under high pressure and relatively low temperature conditions. Albite (NaAlSi3O8) is a common mineral of the Earth's crust, and it has a specific gravity of about 2.6, much less than that of jadeite. With increasing pressure, albite breaks down to form the high-pressure assemblage of jadeite plus quartz. Minerals associated with jadeite include: glaucophane, lawsonite, muscovite, aragonite, serpentine and quartz.
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