Guide to Jade

Jadeite Jade

History, Lore and Appreciation

Jade is a blanket term essentially used to describe two types of gem-quality metamorphic rocks: jadeite jade and nephrite jade. (Henceforth, simply described as jadeite and nephrite). The name for jade (as it is known in the West) comes from the Spanish piedra de hijada, referring to the stones’ shape as they were found, resembling kidneys. In China, appreciation and knowledge about both forms of jade far surpasses that of the West. Since approximately 5000 BCE, the word for jade-like materials, especially nephrite jade, is yu. It is often said that in China, the value and appreciation for jade surpasses that of gold and other gemstones. What the Chinese valued in nephrite was its incredible toughness; as such the gem was often carved into statues, sculptures, hollowed beads, bowls and weapons. The Chinese philosopher Confucius, who was born in 551 BCE, appreciated jade as well, and is widely quoted in regards to the gem:

“The wise liken jade to virtue. Its polish and brilliancy represents purity. Its extreme hardness is intelligence. Its angles, which do not cut, although they seem sharp, are justice. The pure and prolonged sound, which it sings when one strikes it, are music. Its colour is loyalty. Its iridescent brightness represents heaven.”

When jadeite from Myanmar (Burma) became regularly traded with China in the 18th Century, it was an immediate success. China maintains an unparalleled affinity for jadeite, as well as for nephrite jades. Appreciation for jades in the Far East is, in fact, widespread. In Japan, jadeite was already known since the Jomon era, in 3500 BCE.

Enthusiasts of jadeite appreciate its vivid variety of colours including red, orange yellow, green, violet (lavender) and black. (Note: while blue jade is not found in Myanmar (Burma), very small quantities of blue Guatemalan jadeite have been found.) In Central America, one of the other historic sources of jadeite jade, the Mayas and Aztecs appreciated the gem for its hardness and colours as well since before 400 BCE. Today, deep colour and relative transparency are the yardsticks by which both types of jade are measured. Translucent jadeite with a deep uniform green colour sometimes referred to as “Imperial jade,” is especially coveted and collectively known in China as “fei cui”.

Birthstones and Anniversaries

Jade is considered a 12th wedding anniversary gemstone.

Description and Properties

Chemical Composition: Polycrystalline aggregate composed mostly of jadeite that is a sodium aluminium silicate and member of the pyroxene mineral group. NaAlSi2O6

Colour(s): Appearance is semi-transparent to opaque often with mottled colours in white, green, yellow to reddish orange, brown, grey, black, light purple.

Refractive Index: 1.666 to 1.680 (±0.008) Birefringence: Usually not detectable Specific Gravity: 3.34 (+0.06, -0.09)

Cause(s) of colour: In green jadeite: chromium (and /or iron). Iron is the main cause of colour in lavender, orange and brown jadeite.

Mohs Hardness: 6.5 to 7; toughness is exceptional.

Internal identifying characteristics: mottled colours, a granular (sugary) appearance in cracked or unfinished areas of a gemstone.

Treatments

Surface Waxing: Jadeite is sometimes cleaned in acids and neutralizing solutions, followed by boiling in water to clean off any residue. Next, it is dipped in wax as part of the polishing process. The wax enters tiny fissures and pits on the surface of the jadeite, giving the gem a more uniform appearance. Purely natural jadeite (or slightly waxed during polishing) is referred to as “A jade” in the trade.

Acid Bleaching / polymer impregnation: Jadeite with surface stains is submerged in acid to bleach the stains. The treatment causes jade to become more porous; a subsequent polymer resin impregnation renders the jadeite more evenly coloured and translucent. Treatment with acid followed by polymer resin impregnation is referred to as “B jade” in the trade.

Dyeing: Some jadeite is dyed after bleaching, using various colours. Some colours may fade over time, especially when exposed to strong light sources.
As a final step, some jade is then polymer impregnated to make the surface appear homogenous. Such treatments result in jadeite that is referred to as “C jade” in the trade.

Heating: Some jadeite is heated in an effort to change their colour. Heating may lighten some overly dark greens or cause yellow staining to turn a deeper reddish colour.

Collector Quality

Deep natural colour and the homogeneity of the colour plays a large role in the appreciation of jadeite jade. Deep green, translucent jadeite is revered and known in China as “fei cui”, but apple green jade is also highly appreciated. Lavender jade is also popular and rare, while yellow, orange and greyish jade may contain unique symbolic meaning that is linked to their colour. While solid colours in a gem are always appreciated, mottled jadeite jade, where two or more colours can be seen, might be perceived as symbolic and highly coveted. Mottled jade is often used in carvings and they are frequently Chinese in origin because China has a long history of appreciation for jade.

Localities

The classic and most important source of jadeite is Myanmar (Burma), and it remains the principal producer of the gem today. Guatemala is another commercial source, though production is not as sustained as the Asian source. Japan, Russia and Uzbekistan are also sporadic sources of jadeite. Significantly, Burmese jade remains the classic standard by which other jadeite is compared.

Cutting, Care and Cleaning

Jadeite is extremely durable – even though it doesn’t rank as high as some other gems on the Mohs hardness scale. This is because of its extremely compact, fibrous and granular structure. Jadeite
is vulnerable to strong acids and heat. However, assuming the colour is natural and untreated, it is safe for steaming and immersion in an ultrasonic cleaner. If it is not known whether the gem was treated, a soft bristle toothbrush or damp, non- abrasive cloth should be used for cleaning.

Nephrite Jade

Description and Properties

Chemical Composition: Nephrite jade (henceforth simply nephrite) is an amphibole aggregate rock essentially composed by actinolite-tremolite (nephrite) Ca2(Mg,Fe5Si8O22 OH)2

Colour(s): Nephrite can be transparent to opaque, creamy, often with mottled colours in light to dark green, yellow
to brown, white, grey, black.

Refractive Index: 1.606 to 1.632 (+0.009, 0.006)

Birefringence: Usually not detectable

Specific Gravity: 2.95 (+0.15, -0.05)

Cause(s) of colour: iron is the cause of many colours.

Mohs Hardness: 6 to 6.5 hardness; toughness is exceptional, exceeding that of jadeite jade.

Treatments

Surface Waxing: Jadeite is sometimes cleaned in acids and neutralizing solutions, followed by boiling in water to clean off any residue. Next, it is dipped in wax as part of the polishing process. The wax enters tiny fissures and pits on the surface of the jadeite, giving the gem a more uniform appearance. Purely natural jadeite (or slightly waxed during polishing) is referred to as “A jade” in the trade.

Acid Bleaching / polymer impregnation: Jadeite with surface stains is submerged in acid to bleach the stains. The treatment causes jade to become more porous; a subsequent polymer resin impregnation renders the jadeite more evenly coloured and translucent. Treatment with acid followed by polymer resin impregnation is referred to as “B jade” in the trade.

Dyeing: Some jadeite is dyed after bleaching, using various colours. Some colours may fade over time, especially when exposed to strong light sources. As a final step, some jade is then polymer impregnated to make the surface appear homogenous. Such treatments result in jadeite that is referred to as “C jade” in the trade.

Heating: Some jadeite is heated in an effort to change their colour. Heating may lighten some overly dark greens or cause yellow staining to turn a deeper reddish colour.

Collector quality

Deep natural colour and the homogeneity of the colour plays a large role in the appreciation of jadeite jade. Deep green, translucent jadeite is revered and known in China as “fei cui”, but apple green jade is also highly appreciated. Lavender jade is also popular and rare, while yellow, orange and greyish jade may contain unique symbolic meaning that is linked to their colour. While solid colours in a gem are always appreciated, mottled jadeite jade, where two or more colours can be seen, might be perceived as symbolic and highly coveted. Mottled jade is often used in carvings and they are frequently Chinese in origin because China has a long history of appreciation for jade.

Localities

The classic and most important source of jadeite is Myanmar (Burma), and it remains the principal producer of the gem today. Guatemala is another commercial source, though production is not as sustained as the Asian source. Japan, Russia and Uzbekistan are also sporadic sources of jadeite. Significantly, Burmese jade remains the classic standard by which other jadeite is compared.

 

Source: CIBJO Retailer Reference Guide, cibjo.org.