Jade Stone – Characteristics, Varieties, Classification and Cutting

Jade stone is a mineral used since prehistoric times, due to its hardness, it was appreciated for making weapons and instruments.

In China, its use was part of the manufacture of igures and religious symbols used in cults to the gods.

Carved jade stone sculpture
Carved jade stone sculpture

In pre-Columbian Central America, jade was more valued than gold.

In jewellery, around the 17th century, it was discovered that jade was perfect for composing adornments and accessories.

The term jade originates from the Spanish “piedra de ijada”, which means “stone for pain in the side”.

It got its name when the Spanish explorers of Central America saw that the natives used the stone to heal their kidneys.

The Chinese refer to jade as “yu”, which means “heavenly” or “imperial”, and have it as “stone of the gods”.

In China, jade is considered so precious that there is a Chinese saying: “gold is valuable; jade is priceless”. They believe it has health-boosting and longevity-enhancing properties.

The Chinese often carve jade into traditional figures that carry even more meaning, such as dragons, which are symbols of power and prosperity.

In New Zealand, jade also plays an important role. It was used for many years in the making of weapons, chisels and fishhooks.

In 1863, it was discovered in France that the stone known as jade is composed of two species of minerals, which were named jadeite and nephrite.

Bracelet made with jade stone
Bracelet made with jade stone

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As distinguishing the two is difficult, the term jade continues to be used for both forms:

  • Jadeite is tough and hard, composed of sodium silicate and aluminium, in the form of fibres.
  • Nephrite, on the other hand, is made of sodium silicate.
  • Nephrite is a silicate of calcium, magnesium and iron, more resistant than jadeite, formed in reticulated fibrous crystals.

Being rarer, jadeite is more valuable.

Imperial jade is a striking green jadeite, considered the most valuable.

Both jade and nephrite have a beautiful texture, toughness and colours, ranging from pastels to intense, earthy tones and the most well-known green.

In jewellery it is widely used and appreciated.

In the past, some people were so enamoured of it that they became obsessed with it. Throughout the centuries, in historical accounts, jade appears with an important participation, as this obsession ignited wars, such as that of the Chinese Emperor Qianlong who was fanatical about the gem and invaded ancient Burma in search of its deposits.

The Qin dynasty’s collection of sculptures, pieces and jewellery, to which the emperor belongs, is known as one of the largest and most valuable.

Hutton Mdivani jade necklace
Hutton Mdivani jade necklace

The value of jade also encouraged looting of imperial treasures by the French, British and Japanese, as well as adventurers and bandits. It also captivated the rich and famous, who began collecting pieces of the gem – all of which helped drive its price skyward.

And all these stories sparked the idea for a book, the brainchild of two journalists – Adrian Levy and Cathy Scott-Clark, who undertook an ambitious study to show the intriguing history of this valuable gem.

In 1997, “Christie” sold the famous “Doubly Fortunate” jade necklace for almost $10 million and in 2014, that record was broken with the sale of the Hutton Mdivani necklace with ruby clasp by Cartier for over $27 million.

Pedra Jade - Características, Variedades e História

Jade

Gemological characteristics

1. Jadeite

  • Crystalline system: monoclinic, intergrowth aggregates of delicate granules and bireoles.
  • Crystalline system: monoclinic, intergrowth aggregates of delicate granules and bireoles.
  • Chemical formula: NaAlSi 2 O6
  • Hardness: 6 1/2 to 7 mohs
  • Density: 3.30 – 3.38
  • Transparency: translucent, opaque.
  • Colour: green, yellow, white, reddish, lavender, grey and black.
  • Gloss: greasy to pearly.
  • Fluorescence: faint green, greyish blue.
  • Fracture: friable.
  • Refractive index: 1.652 – 1.688.

Jadeite has a characteristic absorption spectrum in the visible light region, observed through the edges in the more opaque gems.

It has a matt lustre on fracture surfaces which, when polished, becomes a greasy sheen.

2. Nephrite

  • Crystalline system: monoclinic, entangled aggregates of delicate fibres.
  • Crystalline system: monoclinic, entangled aggregates of delicate fibres.
  • Chemical formula: Ca2 (Mg, Fe)5  (Si 4 O11)2  (OH)2
  • .Hardness: 6 to 6 /12 mohs
  • Density: 2.90 – 3.03
  • Transparency: opaque
  • .Colour: green, yellow, white, reddish, grey and brown. With frequent spotting.
  • Gloss: greasy to pearly.
  • Fluorescence: none.
  • Fracture: brittle, shattered.
  • Refractive index: 1.600 – 1.627.

Nephrite is an ibreous aggregate variety of the actinolite-tremolite mineral series, so its structure is stronger than that of jadeite.

Most of them have spots and bands, however, specimens with homogeneous colours can be found.

Varieties of jadeite and nephrite

Pure jadeite is white in colour. Both jadeite and nephrite, due to the presence of impurities such as iron and manganese, can be presented in different colours as already mentioned.

The colours tend to be pastel and opaque, with the exception of imperial jade, which has a special lustre and is translucent or semi transparent. Jadeites with uniform colours are more valued.

In the West, emerald green, spinach and green apple are considered particularly valuable.

In the Far East, on the other hand, pure white and yellow with a light pink background, are highly prized.

1. imperial jade

It is a jadeite found in Burma, in Myanmar. It has an emerald green colour from translucent to transparent.

Imperial Jade
Imperial Jade

.It is the most appreciated and sought-after variety, and consequently the most expensive.

This vivid colour is due to the presence of chromium. Some specimens may have small black inclusions.

In terms of size, they are smaller but perfect.

2. Yünan jade

This is the Chinese name given to jadeite, due to the name of the Chinese province through which jade was imported from Burma.

These are lower quality jadeites when compared to imperial jade.

They are found in northern Burma in secondary deposits as conglomerates or pebbles. They are also presented in layers interspersed with serpentine.

3. Grey jade

Nephrite is often referred to simply as jade.

Its colours are less delicate and pure than those of jadeite. They range from dark green (with iron oxide) to pastel colours (rich in magnesium).

They can be mottled, banded or homogeneous.

The typical colour of nephrite is sage or spinach green.

Yellow Jade
Yellow Jade

.The very dark green colour appears to be black. If the nephrite fibres are aligned in parallel, it is possible to achieve a chatoyance effect (cat’s eye effect, sparkle), which is not achieved in jadeite due to its granular composition.

4. Coloured jades

  • Yellow jade
  • Albite jade – Two varieties go by this name. One is a mixture of jadeite and albite, it is green with black spots, it comes from Burma. The other is a chloromelanite. It is composed of kosmoklor, a material related to jadeite, combined with albite, jadeite and other minerals. The presence of chlorite gives it a deep green colour, with dark green veins and spots. It is also found in Burma.
  • Nephrite jade
  • Red jade

    Grey Jade
    Grey Jade
  • White Jade
  • Black jade

Colour and Dyeing

Jade is often subjected to treatments. It can be bleached with acid to remove pigments or stains.

This treatment causes the gem to become more porous and more prone to breakage, so the fractures are usually filled with a polymer, which improves its appearance.

This treatment, or even a dyeing, can be checked with a “Chelsea screen” (a screen that was developed to distinguish pure emeralds from imitations, but is often used for other gems).

Red Jade
Red Jade

Although a large amount of jade is treated, it is not difficult to find natural jades.

Classification

The Chinese jade industry uses a grading system to categorise them according to the amount of enhancements they have received.

This jade grading system is described in grades – from A to D:

  • Grade A – the jadeite is not dyed or filled, but may have received a coating, it is considered stable.
  • Grade B – may have been filled and bleached but is not dyed.
  • Grade C – dyed and filled.

    Cut Jade Stone
    Cut Jade Stone
  • .Grade D – not a natural jade.

Lapidation and Application

Jade is extremely versatile and can be both cut and carved, even into intricate shapes.

It is carved into a variety of traditional Chinese igures, such as Buddhas, dogs, dragons, bats and butterflies but also into rounded, geometric shapes, in short, it has many possibilities that vary according to the design of the piece that will use it.

Other options, carved from pebbles and gravel, are beads, in the form of pearls for rings, brooches and pendants.

Entire bracelets are also made from jade.

Most jades are cut in Taiwan, China and Hong Kong.

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