Its green color comes from iron content; its name, from Spanish. Here's something I read from the Encyclopedia of Word and Phrase Origins:

"Spaniards in medieval times believed that this gem helped cure kidney ailments. They called it piedra de ifada, "stone of the side," which became shortened and corrupted in English to jade. The jade of old horse or a worthless woman, and the adjective jaded derive from another unknown word, of Middle English origin."

Now that's something to chew on. That unknown derivation. I suppose we know that word was Middle English because it must be found in Middle English writings, but we haven't been able to determine from whence it came. It simply erupted into usage.

Correcting a typo, it's piedra de ijada, not ifada.

AHD says of the other jade that it's akin to Swedish dialectal jälda, mare, possibly of Finno-Ugric origin. Sounds like something that might have slipped into the language during the time of the Danelaw.

It wasn't my typo--it's a typo in the edition of the encyclopedia I cited above, p. 365, 1997. I have no Spanish.

Now, now, Dub'. I din't never say whose typo it was; I jes oney corrected it.

Yay - a 'rocky' topic!!

dubdub - you may wish to explore the characteristic of 'toughness' in relation to materials science - and in this case, gemmology. (See Post Edit below)

The crystals in jade are, at a microscopic level, fibrous - brought about by their elongate nature.

So, in contrast to many other crystalline materials, jade doesn't cleave readily. Consequently it can be both a dream and a nightmare to an artisan.

The lack of ready cleavage means that intricate fine detail is possible and that jade is suitable for tasks not generally considered the domain of minerals and rocks. The Maori picked up on this - jade was a favourite material for war clubs.

It's a bit of a nuisance for artisans as it is difficult to polish. Not saying it can't be done, but it is difficult - poor polishing will pit the surface rather than take it back evenly.

stales

POST EDIT: Since making this post I found the following at the South Australian Dept. of Primary Resources web site. Ties together what I wrote above and sjm's reply below.

Nephrite Jade

Jade has been used and appreciated by humans for thousands of years. It was fashioned into ornaments, tools and weapons by Neolithic people and has been used for religious tokens by Aztec, Maya and Maori cultures. The Chinese have revered jade above all other gemstones and it has a unique place in Chinese history. Jade artefacts have been found at ancient sites of Neolithic culture in Europe, Asia, and both North and Central America. Some of the oldest sites, such as one in Siberia, extend man’s use of jade back beyond 5000 BC.

The term jade is used to describe two distinct minerals — nephrite and jadeite. Both materials are tough, compact and fine grained. They may be similar in appearance, but belong to different mineralogical groups. Nephrite jade belongs to the amphibole group, and jadeite belongs to the pyroxene group.

Nephrite, the traditional Chinese jade, is a monoclinic amphibole that ranges between the end members tremolite (Ca2Mg5Si8O22(OH)2) and ferroactinolite (Ca2Fe5Si8O22(OH)2). Nephrite can be white, yellow, green and brown to black, depending on the amount of iron substituting for magnesium. Iron-poor tremolite is white, grey or green; whereas iron-rich varieties (actinolite) are darker green, grey-green, and grading though to black.

The most important property of nephrite jade is its toughness, which explains its widespread use for axe heads, knife blades, and delicate, durable carvings. Toughness in this context is the opposite of brittleness, and is a quite different property to hardness, which is simply the resistance of a material to scratching. Diamond is the hardest mineral, whereas nephrite is the toughest, rivalling modern artificial zirconium ceramics. The toughness of nephrite is due to its interlocking meshwork of fine fibres or needle-like crystals which are commonly 0.1–5.0 µm (microns) in diameter and 20–150 µm long. These fibres usually are arranged in bundles, with the toughest nephrite having bundles of very fine fibres arranged in random interlocking orientation. Coarse grain size and the presence of foliation (alignment of fibres or fibre bundles) reduces the toughness of nephrite.

>The Maori picked up on this - jade was a favourite material for war clubs.

Indeed - the nephrite jade found in the South Island was and is highly prized by Maaori - the Maaori name for the South Island is "Te Wai Pounamu" - literally, "The Waters of Greenstone." All rights to mine and sell pounamu have been ceded to Ngai Tahu, the South Island tribe.

The Chinese have revered jade above all other gemstones and it has a unique place in Chinese history.

For the Chinese and Japanese, jade brings good fortune.

In classical Chinese (Ming Dynasty) water gardens, the inspiration for Japanese water gardens, the natural color of the water is prized because it is the color of jade.

North Americans have imported the passion for Japanese water gardens but expunge all evidence of algae, insisting that their ponds remain unnaturally crystal clear.

Paradoxically, this extra work results in a loss not a gain, the Chinese would say.

In reply to:

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The most important property of nephrite jade is its toughness, which explains its widespread use for axe heads, knife blades, and delicate, durable carvings. Toughness in this context is the opposite of brittleness, and is a quite different property to hardness, which is simply the resistance of a material to scratching.

---

So, toughness isn't hardness; toughness is opposite brittleness. Well, what exactly is toughness? Is it simply that it doesn't fall apart upon impact? You club somebody in the head with your jade club, and it stays in one piece, although another club of another material might have hit the person in the head with a harder wallop?

By the way, thanks, Stales.

Well, Dubdub (she said stepping with trepidation onto the realm of the expert who is absent at the moment), yes, I think your walloping story is on target--jade (nephrite, let me hasten to specify) won't shatter easily. A clue might be its monoclinic property: Of or relating to three unequal crystal axes, two of which intersect obliquely and are perpendicular to the third. (From Atomica.)

Oh, and yes, thanks, Sweet stales!

In the right hand corner we have WW with a jade club and in the left hand corner we have Jackie with three unequal crystal axes. Place your bets on the outcome of this bout, ladies and gentlemen.

Round 1, (ding, ding)

Bingley

Axes! That's a good one, Bingley! stales, sure wish you'd comment on my conjecture (cross-threading neatly!).

Just to stick my neck out for 'Stales to use his jade ax, (or axe) I suspect that jade is in
some sense a composite, that tiny linear elements keep it from shattering.

Edie: Ain't the ;Internet wonderful! I found a site that corroborates my conjecture:
"
Type B jade, bleached, polymer impregnated jade. To distinguish Type B jade, you
need to know the structure of jade as well as the principle and procedure of the
processing of Type B jade. We know that the chemical composition of jade is
NaAlSi2O6, which is composite with columnar crystals and the interlocking structure
made it to be a very tough mineral stone. Because of oxygenation and hydrolysis,
oxides such as iron, manganese and calcium are adhered on the surface and even
immerge into the interspaces between crystal, which turn the color of the jade into
orange, brown, black, or grew. These impurities influence the transparency, as well as
the color of the jade. The purpose of using powerful acid such as sulfuric acid and
chemical on the jade is to remove these impurities, improve the transparency and to
make the green color of jade uninfluenced by the varied colors (caused by the chrome
and iron ion), which make it more delicate and charming (the green color is the original
color of the jade which cannot be removed and affected by powerful acid). Sometimes
the acid is heated to increase its strength. After the jade has been chemically
bleached to remove impurities, it will then impregnated with polymer to enhance
translucency. Polymer is injected into the jade with the use of a centrifuge. At this
stage the jade is covered with hard and clear plastic like coating."