Jade: Gemstone, Types, Properties, Occurrence

Jade, a gemstone revered for its timeless beauty and cultural significance, has captivated the hearts of civilizations for centuries. Jade is a term used to describe two different types of gemstones: nephrite and jadeite. Nephrite is a silicate of calcium and magnesium, while jadeite is a silicate of sodium and aluminum. Both minerals are found in a variety of colors, including green, white, yellow, brown, and black.

Jade: A beautiful Material of nephrite or jadeite

Jadeite is a sodium-rich aluminous pyroxene; nephrite is a fine-grained, calcium-rich, magnesium, iron, aluminous amphibole. All jade is composed of fine-grained, highly intergrown, interlocking ("matted" or "felted" texture, like asbestos or felt) crystals of one or both of these minerals.

Jade is one of the toughest gem minerals known because of the intergrown nature of the individual crystals. The more precious kind of jade, this is a microcrystalline interlocking growth of crystals (not a fibrous matrix as nephrite is.) It only occurs in metamorphic rocks.

The 18-ton Polar Pride boulder was discovered at the Polar mine in 2000, Canada.
Photo: Jade West Group

The two jade minerals, nephrite and jadeite are both tough and have small granular crystals giving a fibrous appearance. They have quite different chemical compositions and structures. Nephrite is a type of amphibole mineral and jadeite is a type of pyroxene mineral. Nephrite can be white, yellow, green and brown to black, depending on the amount of iron and magnesium in the mineral. Jadeite can be green, pink, purple, brown and white.

Nephrite jade is very tough, the toughest known natural mineral, three times tougher than ceramics and even tougher than steel. This explains why it was used in neolithic times for knife blades, axe heads and later for ornamental carvings. While it is not as hard as some other minerals like diamond, nephrite is made from an interwoven meshwork of fine fibres or needle-like crystals so is not brittle and does not break easily. Coarser crystals and alignment of minerals decreases the toughness of the mineral. Jadeite is the second toughest mineral known, but is not as tough as nephrite as its interlocking crystals are less fibrous.

Nephrite is by far the more common form of jade. Nephrite ranges in color from mid to dark green or grey-green, but it can also be white, yellowish or reddish. Nephrite is slightly softer than jadeite.

imperial jade gemstone

The rarest and most valuable jadeite is called imperial jade, colored by traces of chromium. It has color and transparency rivaling fine emerald, though imperial jade is slightly more yellow in tone than emerald.

Properties of Jade

Composition: Jade is a silicate mineral, meaning it's made up of silicon and oxygen atoms bonded together. There are two main types of jade:

Nephrite: Composed mainly of the mineral tremolite, with a Mohs hardness of 6-6.5. It's typically white, green, or grey.
Jadeite: Composed mainly of the mineral jadeite, with a Mohs hardness of 6.5-7. It comes in a wider variety of colors, including green, white, lavender, and even red.

Color: Jade comes in a wide variety of colors, including green, white, lavender, yellow, brown, and black. The most valuable jade is typically a deep emerald green. The color of jade is caused by the presence of impurities, such as chromium, iron, and manganese.

Luster: Jade has a vitreous to greasy luster, meaning it can be glassy or waxy-looking.

Crystal system: Both nephrite and jadeite belong to the monoclinic crystal system.

Streak: Streak refers to the color of a mineral when powdered. Jade has a white streak.

Hardness: Jade has a Mohs hardness of 6-7, meaning it can scratch glass but not steel.

Cleavage: Jade has poor to no cleavage, meaning it doesn't break along specific planes easily.

Crystal form: Jade can occur in massive, granular, or fibrous forms.

Density: Jade has a density of 3.2-3.3 g/cm³, meaning it's slightly heavier than water.

Transparency: Jade can be translucent to opaque. Nephrite is typically more opaque than jadeite.

Fracture: Jade has a conchoidal fracture, meaning it breaks with smooth, curved surfaces.

Specific Gravity: Specific gravity is the weight of a substance compared to the weight of an equal volume of water. Jade's specific gravity is 3.2-3.3.

Solubility: Jade is insoluble in water and most acids.

Magnetism: Jade is not magnetic.

Fluorescence: Fluorescence refers to the ability of a mineral to emit light when exposed to ultraviolet radiation. Jade can exhibit weak fluorescence in some colors.

Pleochroism: Pleochroism refers to the ability of a mineral to show different colors depending on the viewing direction. Jade can exhibit weak pleochroism in some cases.

Refractive Index: Refractive index is a measure of how light bends when passing through a substance. Jade has a refractive index of 1.65-1.67.

Jadeite (left) and Nephrite (right).

Formation of Jade

Jadeite and nephrite are only found in metamorphic rocks, formed in current or ancient subduction zones. Jadeite is found in rocks that formed under higher pressure than nephrite. Most known deposits of jadeite occur along, or near faults in serpentinites. Examples of this type of deposit are found in Myanmar, New Zealand, Canada, Taiwan, Guyana, Surinam, southern Europe, Russia and China. In Australia, nephrite is mostly found as long lenses, within marble of Early to Middle Proterozoic age (2500 - 1000 million years ago).

Nephrite is common products of low-level regional metamorphism (green shale facies), and contact metamorphism of basic and ultrabasic rocks and dolomites. Nephrite consists of a microcrystalline interlocking fibrous matrix of the calcium, magnesium-iron rich amphibole mineral series tremolite (calcium-magnesium)-ferroactinolite (calcium-magnesium-iron). The middle member of this series with an intermediate composition is called actinolite (the silky fibrous mineral form is one form of asbestos). The higher the iron content, the greener the colour. Tremolite occurs in metamorphosed dolomitic limestones and Actinolite in metamorphic greenschists/glaucophane schists.

Where is Jade Found

Jade is found in many parts of the world, but the most significant deposits are found in:

Myanmar (Burma)

Myanmar is the world's largest producer of jade, and is known for its high-quality jadeite jade. The most significant jade deposits in Myanmar are found in the Kachin State, in the northern part of the country.

China

China is also a major producer of jade, and is home to some of the world's oldest jade mines. The most significant jade deposits in China are found in the Xinjiang Autonomous Region, in the northwestern part of the country.

Canada

Canada is the world's second largest producer of jade, and is known for its high-quality nephrite jade. The most significant jade deposits in Canada are found in British Columbia, in the western part of the country.

Russia

Russia is another major producer of jade, and is known for its wide variety of jade colors. The most significant jade deposits in Russia are found in the Eastern Siberia region, in the eastern part of the country.

Australia

Australia is the world's fifth largest producer of jade. The most significant jade deposits in Australia are found in the Northern Territory, in the northern part of the country.

New Zealand

New Zealand is also a major producer of jade, and is known for its pounamu jade, which is a type of nephrite jade that is sacred to the Maori people.

Green nephrite jade

Nephrite Jade: Trade Names

Black nephrite jade

Black nephrite jade a generic term referring to all black or almost black nephrite jade, which is usually caused by microscopic inclusions of dark minerals, mainly graphite.

Hetian Jade

Hetian Jade is one of the classic Chinese jades. It consists almost entirely of tremolite, but can contain up to 5% by weight of impurities such as diopside, epidote, clinozoisite, olivine, dolomite, quartz, magnetite, pyrite, apatite, limonite and carbonaceous matter.

Kunlun Jade

Kunlun Jade is one of the classic Chinese jades, also known as "Qinghai Jade". It consists of actinolite and tremolite in varying proportions, and generally also contains minor wollastonite. The most precious specimens have green-white patterns.

Lantian Jade

Lantian Jade is a variety of tremolite (white jade), which varies in color from white to yellow, gray, pale blue and light green. The colors are due to the inclusions of iron oxides (yellow), graphite (gray) and chlorite, epidote or minerals of the serpentine group (pale blue).

Manasi Jade

Manasi Jade is a green jade which consists mainly of tremolite with only minor actinolite. The green color is caused by microscopic inclusions of green silicates, mainly chlorite and minerals from the serpentine group, and it also frequently contains diopsides and grossulars.

Meiling Jade

Meiling Jade is a typical tremolite jade, in a variety of colors from white to gray. The white varieties are the most precious.

Tremolite Jade

Tremolite Jade is a generic term, referring to all varieties of nephrite which consist mainly of tremolite. While all white jades are tremolite jades, not all tremolite jades are white.

Xiuyan Jade

Xiuyan Jade is a green jade, which contains both tremolite and actinolite in varying proportions. Some varieties may also contain antigorite (Zhang, 2002). One of the classic Chinese jades.

Jade jadeite: trade names

Fei cui jade

Fei cui jade is the most popular variety of jade jadeite. Rarely also blue, lavender-purple, black, red or yellow, depending on the impurities.

Fake Jade

Fake Jade is a Green ornamental stones commonly mistaken for jade

Transvaal Jade: A compact variety similar to green grossular jade containing up to 25% zoisite. Often called "hydrogrossulaire", the water content may be due to the zoisite component rather than a real hydrogrenate.
Queensland Jade: is a natural green to yellow chrysoprase grown in Queensland, Australia.
California jade: is an idocrase (vesuvianite), extracted in the Butte County, near Chico, in California, it is a translucent yellow-green stone also called "californite", it is proposed as an alternative to jade.
African jade: is the other name for buddstone, a variety of fuschite and green serpentine from South Africa.

Conclusion

Jade's enduring popularity can be attributed to its unique combination of beauty, rarity, and cultural significance. As we continue to appreciate and celebrate the rich history of this exquisite gemstone, it is evident that jade's allure transcends time and borders. Whether adorning royal regalia in ancient China or gracing the contemporary jewelry designs of today, jade remains a symbol of elegance, prosperity, and enduring beauty.