Nephrite
Nephrite is one of the two minerals sold as jade, the other being jadeite. It is a calcium magnesium iron silicate belonging to the amphibole group (the tremolite-actinolite series). It is made of tightly interwoven, fibrous crystals, which make it even tougher than jadeite, although it is slightly softer. Polished nephrite has a soft, slightly oily (greasy) lustre.
Nephrite is most often green, from pale to deep spinach green, but it also occurs in white, cream, yellow, brown, grey and black, often mottled. Translucent creamy white nephrite, known in China as "mutton-fat jade", is particularly prized. Darker greens contain more iron.
The name comes from the Latin "lapis nephriticus", meaning kidney stone, from the old belief that the stone could cure kidney ailments. Nephrite is the jade of ancient China, carved for at least 7,000 years into ritual objects, tools and ornaments, and valued above gold and silver. In New Zealand, nephrite is known as pounamu or greenstone and is a treasure (taonga) to the Maori people, who carved it into tools, weapons and pendants such as the hei-tiki.
Most nephrite now comes from British Columbia in Canada, Siberia in Russia and China, with other sources including New Zealand, Australia, Taiwan and the USA. Nephrite is generally untreated apart from waxing, but it may be dyed. Many other green stones are sold as "jade", including serpentine, aventurine, dyed quartzite and glass.
Nephrite at a glance
| Colour | Green, white (mutton-fat), cream, yellow, brown, grey, black; often mottled |
|---|---|
| Hardness (Mohs scale) | 6 – 6.5 |
| Composition | Calcium magnesium iron silicate (amphibole) |
| Crystal structure | Monoclinic; fibrous interwoven aggregate |
| Lustre | Greasy to vitreous when polished |
| Transparency | Translucent to opaque |
| Where it is found | Canada (British Columbia), Russia (Siberia), China, New Zealand, Australia, Taiwan, Poland and USA |
| Wedding anniversary | 35th |
Caring for nephrite
Nephrite (6 – 6.5 on the Mohs scale) is extremely tough and resistant to breaking, so it is suitable for everyday wear, though it can scratch. Clean it with warm soapy water and a soft cloth, then dry. Avoid ultrasonic and steam cleaners, harsh chemicals and high heat, especially if the stone may be dyed or waxed. Store separately from harder stones.
In folklore
The beliefs below are traditional folklore, included for interest. They are not scientifically proven, and nothing here is medical advice.
In ancient China, nephrite jade was considered the "stone of heaven", symbolising virtue, purity and immortality; it was buried with emperors and nobles, sometimes as complete jade burial suits. Confucius compared the qualities of jade to the virtues of a gentleman. In Maori tradition, pounamu pendants are passed down through families and gain spiritual power (mana) over generations. Jade is the traditional gift for a 35th wedding anniversary and is associated with the zodiac signs Libra, Pisces and Virgo.
Jade is traditionally regarded as a stone of harmony, good luck and protection. Crystal healing lore holds that nephrite is particularly protective, keeps the wearer safe from harm and brings balance and calm. It was long believed to help the kidneys. It is linked to the heart chakra.
Related stones
Jadeite (the other jade mineral), tremolite and actinolite. Stones sold as or confused with jade include serpentine ("new jade"), bowenite, green aventurine ("Indian jade"), dyed quartzite ("Malaysian jade"), prehnite, chrysoprase and glass.
For the technically minded
| Scientific name | Ca2(Mg,Fe)5Si8O22(OH)2 |
|---|---|
| Density | 2.90 – 3.10 |
| Refractive index | 1.600 – 1.627 |
| Double refraction | Not usually detectable |
| Cleavage | None (in massive form) |
| Streak | White |
| Fluorescence | Generally inert |