Jadeite

Jadeite
Jadeite from Myanmar
General
Category	Pyroxene group
Formula (repeating unit)	NaAlSi2O6 or Na(Al,Fe3+)Si2O6
IMA symbol	Jd[1]
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, purplish blue, greenish white, white, black, 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[2]
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[2]
References	[3][4][5]

Jadeite is a pyroxene mineral with composition NaAlSi₂O₆. 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.