Jade
​Jade is found in many countries around the world. But in the past, two different minerals were confused and both were called jade, and many more were offered as jade which were fakes! So I’ll do my best to explain the situation.

Jadeite
​The first mineral discussed is Jadeite. Its chemical composition is NaAlSi2O6 in case you are interested. This is a silicate and a member of the Pyroxene group of minerals. Distinct crystals are rare and jadeite is most often found as a tough, compact, granular mass without defined cleavage surfaces. It has a hardness of 6 – 7 and is generally light to dark green, white or yellow with varying degrees of translucency. This is the classic Chinese jade used by that culture since high quality nephrite (the other jade, discussed below) ran short some two to three hundred years ago, although today there is a lot of British Columbian nephrite imported into China and the carving culture is again based on that.

On a general note I must pay tribute to the carvers who, for more than 8000 years, have produced such exquisite carvings, whether for war, daily use or art. The Imperial Green Jade has been called “the stone of heaven” (see References – Adrian Levy book). However, I must not forget the jadeite cultures of Central America where carving was also important from 4000 years ago and which produced some wonderful work.​

Jadeite is found in metamorphic rocks associated with serpentine (described below), which has been subjected to high pressures. But I have only carved a little jadeite and will not go further into the subject.

Nephrite
Nephrite, the “other” kind of jade is a problematic name since it again covers more than one mineral. They are also silicates.  The structure of nephrite is described as "felted" where the needlelike crystals are randomly interlocked.  It has a chemical composition in the range between the end-members of tremolite (magnesium rich and tending to be white – grey) and actinolite (iron rich and tending to be greener) mineral-series, with a chemical composition of Ca2(Mg, Fe²+)5Si8O22(OH,F)2. These belong to the Amphibole group of minerals and have a hardness of 5 – 6. Tremolite is associated with thermally metamorphosed siliceous, dolomitic limestones and ultramafic rocks. Actinolite is generally found in schists produced by low to medium grades of metamorphism in basalts, diabase and pelitic rocks. It is often fibrous, and is one type of asbestos (another catch-all name which I won’t go into here).  If you see an asbestos-like fracture filling in a piece of nephrite you are cutting or grinding, please be extra careful to keep it moist and wear a suitable mask. Nephrite is commonly found in lenses associated with serpentine rocks, which are usually dark green to occasionally red, massive and can be platy to fibrous (eg chrysotile, another type of asbestos). But the important thing is that the crystals of nephrite are acicular, fibrous or elongate which interlock and make this stone a very tough one and suitable for making tools.

I read a fascinating, recent description of nephrite formation, which I'll add here.  It is contained in a paper by Lindley & White and is referenced below.  It is a review paper and I have omitted internal references to other papers for clarity.  They state that "[m]ost nephrite occurrences are small, lenticular and bounded by faults" and go on to say that "regardless of the country rock (gabbro-basalt, argillite-greywacke, clastic limestone), is the product of desilication (Si movement to serpentinite) and calcium-metasomatism (Ca movement to country rock) produced by the enclosing serpentinites and formation is a very late-stage event.  The development of nephrite is evidence of high pressure, and the relatively small deposit size suggests that the conditions that caused felting were localised and ... did not persist long in any one place."

The paper goes on to say that "the metasomatic formation of nephrite is a two-stage process requiring unique physical conditions, including a transient environment with low temperatures and anomalously high pressures (equivalent to >20 km depth of burial) and an abrupt decompression to induce felting of tremolite.  In the first chemical stage, a tectonic inclusion within an upward moving mass of serpentinite is for a brief transient period in an environment favourable to the development of metasomatic contact zones.  The increase in density of rocks in the contact zone indicates high total pressure, mainly the result of water pressure.  This is followed by a secondary mechanical process that develops the felted nephritic structure.  The contact zone is moved into an area of different temperature and pressure where reaction cannot be sustained.  This rapid elevation of the contact zone within the fault is accompanied by rapid decompression and escape of water, allowing the amphibolite formed in the reaction zone to expand and explode violently to create the felted texture.  The resulting shattered mass of tremolite is recrystallised as microfibres with random orientation."

All New Zealand (NZ) jade is nephrite. The jades found at Cowell (Australia), in British Columbia (Canada) and Poschiavo (Switzerland) are also nephrite. I carve stone mainly originating from these areas.

Pounamu/Greenstone
If I haven’t lost you yet, here we have another complication! All jade found in NZ is nephrite. But pounamu/greenstone (the names are used, respectively by Maori and Pakeha for any valued green-coloured stone that is used for carving into tools or decorations) includes nephrite and bowenite (known as tangiwai by Maori), which is a beautiful bright green serpentine mineral with high translucency and a hardness of 5.5. Its chemical composition is Mg3Si2O5(OH)4.

Rather than tell you about the different pounamu fields in NZ, and the different types of stone found (eg kawakawa, kahurangi, inanga, kokopu & totoweka), I would do better to direct you to books written by New Zealanders such as Russell Beck, Neil Hanna (see below) or any other of the celebrated NZ carvers.

I hope I’ve not confused you too much?!

But I’m missing something here. I’ve mentioned the science but not the beliefs of Maoridom which are an important piece of the jigsaw. One story relates to the origin of pounamu and is here taken from the Tai Poutini Polytechnic of New Zealand website ([email protected]).

Poutini is the name of the taniwha (water spirit) swimming up and down the West Coast of the South Island protecting both the people and the spiritual essence, or mauri, of the pounamu (greenstone). Poutini guards the mauri (life spirit) within the treasured stone. The mana or spiritual force of pounamu comes from Kahue (or Ngahue) an atua. Poutini as protector of the stone is the servant of Kahue. Poutini once abducted a woman named Waitaiki, from the North Island and fled south pursued by her husband, Tumaahua. He hid with his captive in the bed of the Arahura River but Waitaiki’s husband pursued them. Poutini transformed Waitaiki into his own spiritual essence – pounamu – and fled down the river to the sea. Waitaiki became the ‘motherlode’ of all pounamu. The husband went home grieving. The Poutini Ngai Tahu is the calling given to Kati Waewae, the section of Ngai Tahu connected to the West Coast.

Whatever your beliefs, the beauty of pounamu stands out for me: it fascinates me, draws me to it. The most exciting times when I’m working the stone are when slabbing it because I never know what the cut will expose, and finishing a piece as it just becomes better and better (hopefully!). In-between is the time of concentration and attention to detail, which I also enjoy and find very rewarding.

Fake Jades
There are many, many fake jades around the world:

• Serpentine, (Mg,Fe)3Si2O5(OH)4, is a part of a large group of commonly found hydrous magnesium iron phyllosilicate minerals which vary widely, and which are often red or dark green (see top picture on left).  Apart from the Bowenite mentioned in the section above, they are pretty, but usually too soft for carving 
• Quartz is a mineral which is offered as jade for instance.  See "Australian jade", below
• Beware of  "Australian jade", also known as chrysoprase, a form of chalcedony, which is a form of cryprocrystalline quartz.  It comes in a range of colours including greens and ochres, and one in particular is a gorgeous semi-translucent mid-green which is similar in appearance to Imperial Chinese jadeite (see lower picture on left)
• Another “jade” is at least not usually sold as the real thing – it is Transvaal jade, which is found in Southern Africa. It is chemically a grossular garnet, Ca3Al2(SiO4)3, and is commonly a translucent red – pink – green - white, with attractive banding and other variations, and a hardness of 6.5 – 7 – it's very pretty and a lovely stone!​
​• In NZ there are some unscrupulous dealers who offer foreign nephrite as pounamu
• Another situation I heard of was 6000 year old Chinese nephrite copies being offered as 7000 year old original pieces!​

​So if you are looking for a special piece of jade, take care and only buy from people you trust!

References
    MH Battey, 1972, revised 1975, Mineralogy for Students, Longman
    Russell J Beck with Maika Mason, 1984, revised edition 2002, Mana Pounamu, New Zealand Jade, Reed
    Bruce Cairncross, 2004, Field Guide to Rocks & Minerals of Southern Africa, Struik
​    Len Gale, Greenstone Carving, A skillbase of techniques and concepts, 1997, Reed Books, NZ
    ID Lindley & PJS White, 2022, A review of the occurrence of and potential for jade in the New Guinea Mobile Belt, Australian Journal of                 Earth Sciences, 69 (4), pp 453 - 472
    WR Hamilton, AR Wooley & AC Bishop, 1974, The Hamlyn Guide to Minerals, Rocks and Fossils, Hamlyn 
    Neil Hanna & Diana Menefy, 1995, Pounamu, New Zealand Jade, Jadepress
    Roger Keverne (Editor), Jade, 1991 (1995 edition), Lorenz Books
    Adrian Levy & Cathy Scott-Clark, 2001, The Stone of Heaven: Unearthing the Secret History of Imperial Green Jade,
             Little, Brown & Company
    Steve Myhre, Bone Carving, a skillbase of techniques and concepts, 2000 edition, published by Reed Books, Auckland
    PG Read, 1982, Dictionary of Gemmology, Butterworths