Jadeite is a

pyroxene The pyroxenes (commonly abbreviated Px) are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents ions of calcium (Ca), sodium (Na), iron ( ...

mineral with composition Na Al Si₂ O₆. It is hard (

Mohs hardness The Mohs scale ( ) of mineral hardness is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fair ...

of about 6.5 to 7.0), very tough, and dense, with a specific gravity of about 3.4. It is found in a wide range of colors, but is most often found in shades of green or white. Jadeite is formed only in the

subduction zones Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second pla ...

of continental margins, where rock undergoes

metamorphism Metamorphism is the transformation of existing Rock (geology), rock (the protolith) to rock with a different mineral composition or Texture (geology), texture. Metamorphism takes place at temperatures in excess of , and often also at elevated ...

at high pressure but relatively low temperature. Jadeite is the principal mineral making up the most valuable form of

jade Jade is an umbrella term for two different types of decorative rocks used for jewelry or Ornament (art), ornaments. Jade is often referred to by either of two different silicate mineral names: nephrite (a silicate of calcium and magnesium in t ...

, a precious stone particularly prized in China. Most gem-quality jadeite jade comes from northern

Myanmar Myanmar, officially the Republic of the Union of Myanmar; and also referred to as Burma (the official English name until 1989), is a country in northwest Southeast Asia. It is the largest country by area in Mainland Southeast Asia and has ...

. Jade tools and implements have been found at Stone Age sites, showing that the mineral has been prized by humans since before the beginning of written history.

Name

The name ''jadeite'' is derived (via and ) from the Spanish phrase "piedra de ijada" which means "stone of the side". The

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

version of the name, ''lapis nephriticus'', is the origin of the term nephrite, which is a different mineral that also shares the common name

Properties

Jadeite is a hard, extremely tough, rare mineral of the clinopyroxene family of minerals. Though highly variable in color, it is typically apple-green to emerald-green, or less commonly white or white with spots of green. Occurrences are typically granular or massive; individual crystals are very rare, occurring only as small prismatic crystals in vugs in massive jadeite. Crystals are four-sided or eight-sided in cross section and show perfect cleavage on 10at angles of 87 and 93 degrees. There is also a rare parting on 00 The interlocking crystals of massive jadeite help give it its extreme toughness. Jadeite has a

of 6.5 to 7, slightly less than that of common

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

. Fracture surfaces are sugary in texture, and sparkle from the exposed perfect cleavage on 10 Jade is relatively dense, with a specific gravity of 3.3 to 3.5 in natural specimens. The specific gravity increases with the iron content, and very pure jadeite has a specific gravity of 3.25. The luster is vitreous, or pearly on exposed cleavage surfaces, and the streak is colorless. Jadeite is translucent to transparent. Jadeite is characterized by its green color and tough aggregates of compact fibrous crystals. It can be distinguished from nephrite by its vitreous luster on polished surfaces (polished nephrite has an oily luster) and by its higher density and

refractive index In optics, the refractive index (or refraction index) of an optical medium is the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refrac ...

. Serpentine also has a lower density and refractive index than jadeite. Massive jadeite also characteristically shows a more granular texture than nephrite or serpentinite. Jadeite has a fusibility of 2.5 (making it moderately easy to fuse with a

propane Propane () is a three-carbon chain alkane with the molecular formula . It is a gas at standard temperature and pressure, but becomes liquid when compressed for transportation and storage. A by-product of natural gas processing and petroleum ref ...

flame) and gives a yellow flame color. Pure jadeite has the composition and has the typical clinopyroxene structure. This consists of long chains of

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant f ...

tetrahedra in which each silicon ion is surrounded by four oxygen ions, with two of the oxygen ions shared with neighboring silica tetraheda. The chains are bonded together by aluminium and sodium ions to form the full three-dimensional structure of a jadeite crystal. The aluminium joins pairs of chains (occupying the so-called M1 site) while sodium joins the paired chains to neighboring paired chains (occupying the so-called M2 site). The resulting crystal structure belongs to the monoclinic system, with

space group In mathematics, physics and chemistry, a space group is the symmetry group of a repeating pattern in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of the pattern that ...

''C2/c''.

Chemistry and origin

Pure jadeite has the composition . There is no significant replacement of silicon by aluminium in natural jadeite, and only very limited substitution of

ferric In chemistry, iron(III) or ''ferric'' refers to the chemical element, element iron in its +3 oxidation number, oxidation state. ''Ferric chloride'' is an alternative name for iron(III) chloride (). The adjective ''ferrous'' is used instead for i ...

iron for aluminium. However,

calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...

substitutes for up to 20% of the sodium, balanced by substitution of

magnesium Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...

ferrous In chemistry, iron(II) refers to the chemical element, element iron in its +2 oxidation number, oxidation state. The adjective ''ferrous'' or the prefix ''ferro-'' is often used to specify such compounds, as in ''ferrous chloride'' for iron(II ...

iron for aluminium. Omphacite is intermediate in composition between jadeite and diopside. However, there is not a true

solid solution A solid solution, a term popularly used for metals, is a homogeneous mixture of two compounds in solid state and having a single crystal structure. Many examples can be found in metallurgy, geology, and solid-state chemistry. The word "solutio ...

series, as omphacite has its own structure that is slightly different from either pure jadeite or pure diopside, so that it is separated from either end member by a

miscibility gap A miscibility gap is a region in a phase diagram for a mixture In chemistry, a mixture is a material made up of two or more different chemical substances which can be separated by physical method. It is an impure substance made up of 2 or more ...

. ''Chloromelanite'' is a dark green variety of jadeite in which some aluminium is replaced by iron, while ''imperial jade'', the most valuable variety of jade, is colored an intense emerald green by traces of

chromium Chromium is a chemical element; it has Symbol (chemistry), symbol Cr and atomic number 24. It is the first element in Group 6 element, group 6. It is a steely-grey, Luster (mineralogy), lustrous, hard, and brittle transition metal. Chromium ...

Jadeite occurs with

albite Albite is a plagioclase feldspar mineral. It is the sodium endmember of the plagioclase solid solution series. It represents a plagioclase with less than 10% anorthite content. The pure albite endmember has the formula . It is a tectosilicat ...

metamorphic rock Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock ( protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, caus ...

of the low-temperature, high-pressure blueschist facies at destructive plate margins. Although it is intermediate in silica content between

and

nepheline Nepheline, also called nephelite (), is a rock-forming mineral in the feldspathoid groupa silica-undersaturated aluminosilicate, Na3 K Al4 Si4 O16, that occurs in intrusive and volcanic rocks with low silica, and in their associated pegmatit ...

, it is not stable under the conditions in which these two minerals are present. Formation of jadeite requires a pressure of 10 to 25 kbar and a temperature of via the reaction: Jadeite can also form at high pressure via the reaction: At still higher pressure, corresponding to the highest blueschist facies, jadeite reacts with lawsonite to form zoisite and paragonite: Minerals associated with jadeite include: glaucophane, lawsonite,

muscovite Muscovite (also known as common mica, isinglass, or potash mica) is a hydrated phyllosilicate mineral of aluminium and potassium with formula KAl2(Al Si3 O10)( F,O H)2, or ( KF)2( Al2O3)3( SiO2)6( H2O). It has a highly perfect basal cleavage y ...

aragonite Aragonite is a carbonate mineral and one of the three most common naturally occurring crystal forms of calcium carbonate (), the others being calcite and vaterite. It is formed by biological and physical processes, including precipitation fr ...

, serpentine and

. Rocks that consist almost entirely of jadeite are called jadeitite. In all well-documented occurrences, jadeitite appears to have formed from

subduction zone Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second p ...

fluids in association with

serpentinite Serpentinite is a metamorphic rock composed predominantly of serpentine group minerals formed by serpentinization of mafic or ultramafic rocks. The ancient origin of the name is uncertain; it may be from the similarity of its texture or color ...

. Jadeitite is resistant to weathering, and alluvial boulders of jadeitite released from the serpentine-rich environments in which they formed can have weights of up to tons. Raw specimens having Burmese tax stamps or polished slots for evaluating quality are prized by some collectors.

Colors

Jadeite's color commonly ranges from white through pale apple green to deep ''jade'' green but can also be blue-green (like the recently rediscovered "Olmec Blue" jade), pink, lavender and a multitude of other rare colors. ''Chloromelanite'' is a very dark green to black variety. Color is largely affected by the presence of trace elements such as chromium and iron. Its translucence varies from opaque to almost clear. Variations in color and translucence are often found even within a single specimen.

Occurrence

Significant occurrences of jadeite are isolated and rare. It is found exclusively in high-pressure, low-temperature metamorphic rock of continental margins. Here it may be found as pods or veins or as disseminated grains. Deposits are found in

, the Alps, Russia, California, Japan, and

Guatemala Guatemala, officially the Republic of Guatemala, is a country in Central America. It is bordered to the north and west by Mexico, to the northeast by Belize, to the east by Honduras, and to the southeast by El Salvador. It is hydrologically b ...

. In the

Franciscan Complex The Franciscan Complex or Franciscan Assemblage is a geology, geologic term for a late Mesozoic terrane of heterogeneous rock (geology), rocks found throughout the California Coast Ranges, and particularly on the San Francisco Peninsula. It was n ...

of California, jadeite is associated with glaucophane, aragonite, muscovite, lawsonite, and quartz. However, occurrences of

lapidary Lapidary () is the practice of shaping rock (geology), stone, minerals, or gemstones into decorative items such as cabochons, engraved gems (including cameo (carving), cameos), and faceted designs. A person who practices lapidary techniques of ...

quality are almost exclusive to

. Stream boulders of the Uyu River remain an important source of jadeite.

Uses

Jadeite is the dominant mineral of the most desirable variety of

. This was prized in traditional Chinese culture, where it was worked into a great variety of beautiful ornaments and utensils. Jadeite was also used by Stone Age peoples for implements and weapons. Jade received its name, "piedra de ijada" ("stone of the side"), because it was once thought to cure kidney ailments when applied to the side of the body.

Jade

Jadeite is one of two minerals recognized as the

gemstone A gemstone (also called a fine gem, jewel, precious stone, semiprecious stone, or simply gem) is a piece of mineral crystal which, when cut or polished, is used to make jewellery, jewelry or other adornments. Certain Rock (geology), rocks (such ...

. The other is nephrite. Occasionally, other minerals such as serpentine or

are sold as jade, but the difference can be determined by cleavage and hardness. Jadeite jade is the most valuable form, with the highest-quality material commanding prices well in excess of $200 per carat . Jadeite jade first came into significant use in China only towards the end of the 18th century, as ''fei tsui''. Jadeite from the Motagua Valley,

, was used by the

Olmec The Olmecs () or Olmec were an early known major Mesoamerican civilization, flourishing in the modern-day Mexican states of Veracruz and Tabasco from roughly 1200 to 400 Before the Common Era, BCE during Mesoamerica's Mesoamerican chronolog ...

and

Maya peoples Maya () are an ethnolinguistic group of Indigenous peoples of the Americas, Indigenous peoples of Mesoamerica. The ancient Maya civilization was formed by members of this group, and today's Maya are generally descended from people who lived w ...

, as well as the indigenous peoples of

Costa Rica Costa Rica, officially the Republic of Costa Rica, is a country in Central America. It borders Nicaragua to the north, the Caribbean Sea to the northeast, Panama to the southeast, and the Pacific Ocean to the southwest, as well as Maritime bo ...

. Unusual colors, like "Olmec blue" jade, which is characterized by its deep blue-green, translucent hue with white flecking, are becoming more highly valued because of its unique beauty and historical use by the Mesoamerican

and also in

Stone Age use

Over 180 axe heads made from jadeitite quarried in northern Italy in the

Neolithic era The Neolithic or New Stone Age (from Ancient Greek, Greek 'new' and 'stone') is an archaeological period, the final division of the Stone Age in Mesopotamia, Asia, Europe and Africa (c. 10,000 BCE to c. 2,000 BCE). It saw the Neolithic Revo ...

have been found across the British Isles. Because of the difficulty of working this material, all the axe heads of this type found are thought to have been non-utilitarian and to have represented some form of currency or be the products of gift exchange. A great many jadeite beads and axe heads as well as the remains of jadeite workshops from the

have been uncovered in Itoigawa, Japan. These beads and axes were traded throughout Japan and the Korean Peninsula and were produced by the world's oldest known jadeite-using culture, centered on the Itoigawa region.

References

Sources

External links

* {{Gemstones Sodium minerals Aluminium minerals Pyroxene group Monoclinic minerals Minerals in space group 15 Jade