Technical Characteristics
Jade refers to two chemically different stones: jadeite, a silicate of
sodium and aluminum, and nephrite, a silicate of calcium and magnesium.
Although different, they share many common characteristics. In Europe, the
technical characteristics of the two varieties were first published by
Damour in 1863; the Chinese were aware of the differences long before.
Jadeite, the rarest and most valuable form of jade, is also known as
'Burmese Jade', (after its traditional and still most important source).
It has been in wide use only since the mid-18th century, and today is
considered the 'precious' form of jade. Most 'fine jewelry' items of jade
consist of jadeite. Jadeite exhibits a wide palette of sometimes vibrant
colors, often with translucence. Green is the most valuable color; in
particular, a translucent emerald-green is the most prized of all, and is
sometimes called 'Imperial Green'. Jadeite is also available in lavender,
red, yellow, black and white.
Nephrite, the traditional form of jade, has been used for over 5000 years
by many different cultures throughout the world. It is the Chinese,
however, that raised the craft of jade carving to an art, and who
appreciated it on the deepest levels; the rich mix of mythology and
religion in China seemed to find it's highest expression in the virtues of
jade. Nephrite colors are subdued, and range from grey to brown to
blue-green to black. Translucence is rare. The highest quality comes from
Siberia, and sometimes New Zealand or Australia. Taiwan has good nephrite,
but the giant of all producers today is British Columbia.
Technical-Characteristics
Jadeite
Nephrite
Texture interlocking granular structure
(microcrystalline) interwoven fibrous structure
(cryptocrystalline)
Surface Luster vitreous, sometimes greasy greasy, sometimes vitreous
Fracture Structure granular, possibly splintery splintery, possibly
granular
Refractive Index 1.65-1.68 1.60-1.63
Specific Gravity 3.3-3.8 2.9-3.0
Hardness (Mohs) 6.5-7.0 6.0-6.5 |
