JADE

JADE	One of the toughest gems
Major Sources	Canada (BC), China, New Zealand, Russia, Taiwan
Colors Found	Blue, brown, cream, green, gray, lavender, red, white & yellow
Family	Amphibole: Ca2(Mg,Fe)5(Si4O11)2(OH)2
Hardness	6 to 6.5
Refractive Index	1.60–1.63
Specific Gravity	2.90–3.03
Crystal System	Monoclinic (aggregate)
Enhancements	May be enhanced

For centuries, nephrite jade and the other jade type, jadeite, were considered one and the same. It was not until 1863 in France that they were identified as different minerals with a similar appearance and properties.

The name jade was first used around the time of the Spanish conquest of Central and South America and is from the Spanish piedra de ijada, meaning hip stone, as it was thought to cure kidney stones and other kidney ailments.

While jade was known as the “stone of heaven” in ancient China, the Chinese word for jade, yü, is not generally used. Jade was excavated from the Kunlun Mountains of northwest China, from 5000 BC, and even today China remains an important source for this gemstone.

Legends and lore

In Russia, it has been mined and crafted since 3000 BC. Tsar Alexander III’s sarcophagus was carved from jade. For about 3,000 years jade has been highly prized by the Native Americans of British Columbia, Canada who called it “greenstone” and for centuries the New Zealand Maori have made beautiful nephrite carvings.

Just the facts

Nephrite is composed of silica and magnesia and its color is determined by the amount of iron present in the mineral. A lesser iron content produces lighter colors such as white, cream, yellow, grey, green, blue, red, brown and lavender. A greater iron content produces the darker colored nephrite, such as darker grey and darker green.

Nephrite has the highest tensile strength (toughness as opposed to hardness) of all natural gemstones and even has a tensile strength greater than some steel. It is so strong that it cannot be chiseled. It must be ground using sharp abrasives.

Interestingly, less than 0.05% of nephrite extracted is of gem quality. Nephrite is typically not dyed as it is less likely to take up dye or stains than jadeite. Older pieces benefit from polishing to retain their luster.