Is jade a crystal or a stone?
Jade is a jewelry and semi-precious stone, less commonly used as a decorative collectible geological material. Jade is a rock of metasomatic origin with a cryptocrystalline (hidden fibrous) structure. It has a significantly amphibole mineral composition (more than 85%), represented mainly by minerals of the tremolite–actinolite series. The mineral composition of jade often contains other minerals, which can account for up to 15%. Among these minerals are silicates (talc, serpentine, diopside, titanite, zoisite, minerals of the epidote supergroup, minerals of the chlorite group and others), carbonates (calcite, dolomite), oxides (magnetite, chrome spinels), as well as graphite. Some researchers, based on the common mineral composition and physical properties, classify the jewelry and ornamental stone dianite as jade, which is not entirely correct, since the main rock-forming mineral of dianite is richterite.
The name is jade (Greek word “kidney»-«bud“) was introduced into use by the French naturalist and mineralogist Alexis Damour (Augustin Alexis Damour; 1808-1902), who first established that jewelry and ornamental stones, united by the term “jades” (“ijada stone“), are not homogeneous in mineral composition. He divided these rocks into jadeitites, composed of pyroxene – jadeite, and jades, composed of amphiboles of the series of isomorphic miscibility tremolite-actinolite. Texture: homogeneous, spotted, banded, fluid, other more rare textures are possible; Microtexture: fibroblastic (tangled fibrous, “downy”), parallel fibrous, nematoblastic centric (radial-radiating), nematoblastic, porphyroblastic sheaf-shaped; Color: From white to green and black, with various shades of brown, yellow-brown. The green color is due to the increased content of the actinolite component, as well as the admixture of chromium and vanadium in the rock-forming amphiboles. There are pink-violet colors (mangan-tremolite) as well as blue shades (admixture of alkaline amphiboles – riebeckite, richterite).
Diagnostic properties
| physical properties | |
|---|---|
| Mohs hardness: | 5,5-6,5 |
| Density: | 2,90 – 3,32 g/cm 3 |
| Kink: | splintery |
| Optical properties | |
|---|---|
| Optical character: | unit; |
| Refractive index: | 1,600-1,630 |
| Birefringence: | 0,026-0,027, often absent |
| Dichroism: | faint green to brownish-green may be observed |
| Shine: | glass, frosted |
| Transparency: | opaque to translucent |
Characteristic inclusions and structural heterogeneities
Inclusion of chromite in jade (Ulan-Khodinskoe deposit, Buryatia). Viewing mode – reflected light 
Cr-tremolite with talc inclusions (Emerald Mines, Urals). Viewing mode – reflected light 
Crystal of Cr-tremolite in talc slate (Emerald Mines, Urals). Viewing mode – reflected light 
Inclusions of chrome spinel in jade (Ulan-Khodinskoye deposit, Buryatia). Viewing mode – reflected light 
The characteristic surface of jade in a fracture. Viewing mode – reflected light 
Dendrites of iron-manganese hydroxides along microcracks in jade (Buromskoye deposit, Buryatia). Viewing mode – transmitted light
Basic methods of refining
| Upgrading method | Goal |
|---|---|
| Impregnation | Increased transparency |
| Impregnation | Color change |
| Surface painting | Color change |
| Diffusion treatment (thermochemical dyeing) | Color change |
Synthetic analogues and imitations
- glass and ceramic compositions of artificial origin;
- polymer compositions of artificial origin;
- serpentinites;
- amphibolite and chlorite rocks, calciphyres, marble, agalmatolite and other rocks that are not jade, but look like jade;
- quartzites and other essentially quartz rocks, colored in various shades of green.
Characteristic inclusions and structural heterogeneities
Serpentinite. Variety – bowenite. Viewing mode – reflected light
Serpentinite. Variety – bowenite. Viewing mode – reflected light
Serpentinite. Variety – Bowenite. Imitation Jade (Bazhenovskoye deposit, Middle Urals). Viewing mode – reflected light
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About jade
Although “jade” had been used for a variety of utilitarian and artistic purposes for over 7000 years, it was not until 1863 that a gemological distinction was made between the two different species that received the name. Jadeite, an aggregate of granular pyroxenes, is not actually related to jade, an aggregate of fibrous amphiboles. The fact that they come in the same color and translucency range, are both incredibly durable and have traditionally been used for the same purposes, along with their superficially similar appearance, has led to the strange consequences of having two completely different gemstones with the same name.
Although marketers, jewelers and the public continue to refer to both stones as jade, it is more correct to use this species, or at least include it in the name: so either jade (or jade jade) or jadeite (or jadeite jade) is the preferred terminology.
Thus, jade is a calcium-magnesium silicate that varies from translucent to opaque and from shades of green, through brown and yellow to gray and almost white, as it varies in the proportion of amphibole minerals in its composition. The darker pieces are mostly composed of iron-rich (up to 5% iron content) actinolites, the lighter pieces contain more magnesium-rich tremolites. The pieces may be speckled or striped, and black inclusions are common. Typically, the green colors of jade produced by iron are somewhat dulled by brown tones compared to the richer green tones of jade produced by chromium.
Since nephrite, jade, by definition, is a mixture of amphiboles with an interlocking microcrystalline structure, pure actinolite or pure tremolite minerals are therefore not nephrite. Although actinolite is sometimes found in the form of chateau yant, which is often sold under the incorrect name “cat’s eye jade”.
Jade is mined in many regions, from New Zealand, Siberia and South Korea to the United States (most notably Wyoming and California), but the largest deposits are by far in British Columbia. Huge boulders, often covered in a brown crust of oxidized iron, are common in these Canadian sites. The finest of these materials is branded “Polar Jade” and has a translucent and rich green color seen in very few other jade specimens. Large-scale mining began here in 1995.
The widespread use and beneficial properties of jade explain its worldwide use by ancient cultures. Archaeologists have found jade tools and art in places from Switzerland to New Zealand, America and Asia.
These people valued this stone highly as it could be used to make sharp knives, spears, hammers and axes, and it could also be used to carve exquisitely thin bowls, figurines, masks and jewelry. Its legendary strength is a consequence of the interlocking “felt” nature of the tiny fibrous crystals within. Before the advent of steel, jade was the strongest material for making tools and weapons, less brittle and retaining its edge better than any other stone or copper, bronze or iron.
Although jade artifacts in Europe date back to 3500 BC, there is evidence to support their use in China for over 7000 years. The jade around which the Chinese built many aspects of their culture was technically sourced from Turkestan, a region that was not politically part of China until after World War II. Known in legend as the “Stone of Heaven”, jade achieved a position in the religious and cultural life of these people unmatched by any other natural substance in any other time or culture.
The two pieces shown below are modern Chinese jade carvings. The curled “dragon” is carved from “tomb jade” that has been buried underground for a long time, stained and somewhat corroded by iron minerals. It is made in an exact copy of the style of the Han Dynasty period, approximately 200 BC. E. The white citrus carving is produced in Xinjiang (the traditional harvesting point of rare white jade) and exhibits the purity of color, transparency and desirable “bold” sheen of the finest ancient materials.
Throughout much of China’s 7000-year love affair with jade, jade has been an object of affection and veneration. It was not until 1784 that jadeite was imported into China in large quantities, which led to its rapid “conquest” in popularity.
The Maori of New Zealand had the same initial relationship with jade as the Chinese, if not so long ago. Known as “punamu” or green stone, it was used to make weapons, tools, decorative and religious items. Some of the world’s most advanced jade carvings have been carried out in recent years by New Zealanders using some of the excellent local materials. The fragment below is a superb example from the hands of Donn Salt.
There are three known types of jade produced in the United States: black with magnetite inclusions and “Wonsen blue” jade, both from California, and green to black material from Wyoming.
The name “jade” comes from the early belief that wearing talismans made of certain green stones could cure or prevent kidney ailments, although, ironically, scientists discovered that such a stone was actually jadeite.
However, jade, one of the most widely available gemstones, has been subject to extensive imitation. Natural simulants often represented (consciously or not) as jade include bowenite, vesuvianite, serpentine, aventurine, amazonite, antique green, and massive grossular garnet.
Jade is sometimes enhanced by dyeing, heating, and waxing, although the prevalence of such treatments is not as high as with jadeite gemstones. Imitation artificial glass called “metajad” or “imori stone” is sometimes found on the market, although real synthetic jade is not.
Jade gemstones or art pieces require little care and can be safely cleaned using ultrasonic cleaners.
