Jade

Specific Gravity: 3.33
Refractive Index: 1.66-1.68
Birefringence (DR): 0.012
Luster: Greasy to pearly
Crystal Structure: Monoclinic
Composition: Sodium aluminum silicate
Hardness: 7

Jade was thought to be a single stone for many centuries. However, in 1863, two types were recognized: jadeite and nephrite. Jadeite is made up of interlocking and granular pyroxene crystals. It occurs in a wide range of colors including green, pink, lilac, brown, orange, black, white, yellow, and blue. The most prized variety, imperial jade, has is a rich emerald-green, due to chromium.

Jadeite commonly has a dimpled surface when polished. The Spanish conquistadores adopted the use of Jadeite when they invaded Central America, and often wore amulets made from them. They called it piera de hijada (loin stone) or piedra de los rinones (kidney stone). That is because they believed that it prevented or cured hip and kidney complaints.

Older jadeite carvings have a characteristic pitted surface. However, modern abrasives give it a smoother finish. It is interesting to note that the violet color is caused by traces of iron. Jade is usually carved into beads and cameos.

Table of Contents

Occurrence

Jadeite jade is found in metamorphic rocks and as alluvial pebbles and boulders. Some boulders develop brown skin, due to weathering, and this is often incorporated into carvings and worked pieces. The most important source of jade is Myanmar (Burma), which has supplied China with translucent imperial jade for more than 200 years.

Historically, Guatemala was an important source of jade. It provided the material for the carvings of the Central American Indians. Jadeite also occurs in Japan and California.