Geoarchaeology: Lithic Artifact Mineralogy

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Jades: Jadeite and Nephrite

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Reports in diaries kept by early Spanish explorers document the special status of a gemstone unknown to them, one that would come to be called "jade". Captain Bernal Diaz del Castillo wrote an account of his service to Hernan Cortez entitled The "True History of the Conquest of Mexico" (1568/1632). In Bernal Castillo's history, he attests to the value placed on jade by the Mesoamerican Indians:

"Montezuma also sent four jewels called calchihuis , resembling emeralds, most highly valued by the Mexicans (Aztecs)...these rich jewels...were intended for our emperor..." (p. 59)

"I never was avaricious, and now thought more of saving my life which was in much danger; however when the opportunity thus offered, I did not omit seizing out of a casket, four calchihuis, those precious stones so highly esteemed amongst the Indians;...I luckily secured these jewels in time, and afterwards found them of infinite advantage as a resource against famine." (p. 219).


By 1531, the Conquest of Mesoamerica by the Spanish was so complete that it totally obliterated the 3000 year-old jade industry. This once highly prized gemstone totally disappeared from the traditions of the surviving cultures to the extent that even the sources were lost (Sinkankas, 1959; and Woodward, 1987). Known only from artifacts, it was not until 1952 that Robert Leslie found in-situ jadeite in serpentinites near the village of Manzanal in the valley of the Rio Grande Motagua in south-central Guatemala (Sinkankas, 1959). To date, this region still remains the single known geologic source of Mesoamerican jade (Bishop and Lange, 1993).



The Origin of the Names Given to Jade

The term calchihuis is apparently a Spanish aberration of the Nahuatl word xalxihuitl (Foshag, 1957):

xalil - jewel (or sand) + xihuitl - herb (or herb colored).

This name was not retained for the gemstone, like every other aspect of Mesoamerica's jade tradition, it too slipped into obscurity. In fact, none of the ancient names for jade given by cultures with a jade tradition were used; therefore, names like "yu" (China), "giyuki" (Japan), "punamu" (Maori, New Zealand), "steiu soka-a ist" (Salish), and "tsu" (Tlingit) also fell into disuse (Emmons, 1923, and Strack, 1972).


The term "jade" is apparently a corruption of the Portuguese or Spanish phrase:

"pedra de ijada" - stone of the loins (Desautels, 1971), or

"piedra de hijada" - stone of the flanks (Anderson, 1976), respectively.


During the sixteenth century, the Portuguese and the Spanish were importing "jada" from the Orient, Amazonia, and Mesoamerica, and so named it because of their superstitious belief that "jada" could cure urinary diseases. The phrase was translated into Latin: "lapis nephriticus" (Foshag, 1957, and Desautels, 1971). In 1863, the famous French chemist, Augustin Alexis Demour, realized that jades obtained from distant sources were actually composed of 2 different types of material and he named them "nephrite" (fine-grained, felted variety of tremolite-ferroactinolite series {Ca2[Mg,Fe]5Si8O22[OH,F]2}) and "jadeite" (a new mineral [NaAlSi2O6]) (Moriarty, 1973, and Anderson, 1976). These two materials, even though quite different in appearance, composition, petrogenesis, and abundance, are both still considered to be true jade by modern gemologists (Schumann, 1997). In geology, however, the term "jade" has no exact meaning and is not used. In summary, "jade" is a gemological term and has no exact meaning in geology and mineralogy.


The Aztecs and other contemporaneous and preceding Mesoamerican Indian Cultures, Dynastic China, and many other cultures around the world utilized several different types of greenstone for tools and ornaments including nephrite, jadeite, jadeite-related minerals like omphacite and chloromelanite, albite and other feldspars, serpentine, chalcedony, and talc (soapstone, steatite). Ancient classification systems may have existed differentiating types of jade into categories based on physical properties such as color, diaphaneity, luster, hardness, toughness, density, and texture (Foshag, 1957), apparently matched by these criteria rather than by mineralogy. All lapidary-grades of available greenstone may have served the same purpose making the Mesoamerican concept of "xalxihuitl" and the Chinese concept of "yu" quite different from modern Western gemologists ideas regarding jade. "Xalxihuitl" in Pre-Columbian Mesoamerica and "yu" in Dynastic China represented strength in tools and weapons, beauty and value in gemstones, emblems of status and rank in regalia, the ultimate medium in sculpture, important symbols and components in religious and mortuary ceremonies, and of life in the color of crops and water. In the material and spiritual sense, jade was omnipotent to these early cultures. It is very difficult to evaluate and appreciate the true nature of the relationship ancient Mesoamericans and Chinese had with jade because we lack its counterpart in our modern society.


Jade: The Quantum Leap from Toolstone to Gemstone

Jades (jadeite and nephrite) are unique among rocks distinguished from all others by their extreme tenacity, moderate hardness, and high density. Tenacity is a measure of a rocks toughness and resistance to breakage. Nephrite jade is the toughest naturally occurring substance on Earth and jadeite jade is second only to nephrite jade with respect to its resistance to breakage. When a boulder of jade is struck, hammer falls are deflected and the boulder rings like a bell.

Hardness is resistance to scratch and jades have a hardness of 6 to 7 (1 being the softest, 10 the hardest) typical of silicate minerals. Therefore, like steel, jade is very difficult to break but not hard to scratch. This combination of extreme tenacity with moderate hardness makes the material ideally suited for percussion tools like axe bits and adz blades, needle-like tools such as perforators and drill bits, and farming implements like hoes. Jade is relatively easily shaped due to moderate hardness (workability) and tough enough to persist under use due to extreme tenacity (serviceability) (Dunning, 1960). Jade is also a dense rock at 3.0 to 3.2 g/cm3 for nephrite and 3.3 to 3.5 g/cm3 for jadeite compared to most continental crustal rocks with densities between 2.5 to 2.7 g/cm3. Jade's high density increases the momentum developed when swinging an axe with a jade bit creating a greater force of impact. In summary, jade is the toolstone par excellence .

When used, jade axe bits and drill tips take on a natural polish due to use-wear. That the material takes and holds a high polish that reveals its inner beauty, translucent diaphaneity, and range of colors set jade apart from other workable and serviceable greenstones. Its beauty lead to recycling of spent tools into simple ornaments. This
general pattern is seen practically everywhere jade was available to early cultures. So valuable was jade by Aztec times (late Post-Classic Period), that its ownership was regulated by a code of laws (Peterson, 1959):

"The Aztec Laws demanded that anyone who stole jade ornaments be stoned, because no man of low quality might posses jade." (p.227).


Even the procurement of jade in Mesoamerica took on a supernatural flavor (Peterson, 1959):

"Finding jade was a special talent among the Aztec, who said that they located it by standing on a hill on a misty morning and watched the vapours rise from the stones. When a certain vapour arose from a stone its nucleus was probably of jade." (p. 227).


By the time of the Conquest of Mesoamerica and the time of contact with Dynastic China, jade had been transformed from the toolstone par excellence to the noble gem without equal. Jade's status as the sacred medium of religious iconography, its use in regalia symbolizing wealth and power, the industry employing merchants and craftsman, and the conventions governing its use all arise from its unique combination of physical properties: extreme tenacity, moderate hardness, translucent diaphaneity, range of colors, high density, and vitreous luster. Jade, the rock that is cool to the touch, that chimes like a bell when struck, truly stands apart from all other rocks, minerals, and gemstones.


The Mineralogy of Jade

A mineral is a naturally occurring, inorganic, crystalline solid with a definite chemical composition. Rocks are naturally occurring, coherent aggregates of minerals. Jadeite jade and nephrite jade are both aggregates of mineral grains; therefore, they are rocks. Unlike most rocks that are composed of several minerals, jadeite jade and nephrite jade are composed predominantly of one mineral (monominerallic): jadeite and tremolite-ferroactinolite, respectively.

Nephrite is the compact (no porosity), microcrystalline (very fine-grained), fibrous variety of the tremolite-ferroactinolite series in which the fibers are interwoven into a tough, felted aggregate; therefore, nephrite describes a type of texture as well as a gemstone and a rock type. Samples of tremolite-ferroactinolite can be considered nephrite only if their fine-grained fibrous crystals form a uniformly matted, interlocking network (nephritic texture). Nephritic texture produces a massive, nonfoliated, even-textured rock that is the toughest of all known rocks (and naturally occurring materials) requiring as much as 90,000 lbs/in2 to crush a sample! Tremolite-ferroactinolite belongs to the amphibole mineral group and the monoclinic crystal system, it has a hardness that ranges from 6 to 6.5 on Mohs scale of hardness, and it has a waxy to sub-vitreous luster (Dorling and Zussman 1985, Rizzo 1982, and Ward 1987).

Tremolite (Ca2Mg5Si8O22[OH,F]2) and ferroactinolite (Ca2Fe2+5Si8O22[OH,F]2) form a solid solution series where the pure end members rarely (if ever) form; instead, what usually forms is a mineral called actinolite with an intermediate composition (Ca2[Mg,Fe2+]5Si8O225Si8O22[OH,F]2). Densities range from 3.0 g/cm3 to 3.5 g/cm3 with increasing iron content; however, all of the nephrite samples that I have analyzed have densities that range from 3.0 g/cm3 to 3.2 g/cm3 . With increasing iron content, tremolite-ferroactinolite changes from white to green to greenish black (Deer et al. 1963). Nephrite forms under greenschist metamorphic conditions (4 - 5.5 kbars of pressure at approximately 400oC). In summary, nephrite cannot have a density less than 3.0 g/cm3 because it is a monominerallic, nonporous aggregate of actinolite, and with increasing iron content the density increases (as does refractive index) and the color changes from white to green.

Nephrite is the jade that was used exclusively by the following cultures: early to mid-Dynastic China, prehistoric New Zealand, prehistoric Alaska and British Colombia, prehistoric Brazil, and pre-Celtic Europe. Nephrite jade does not occur in Mesoamerica; therefore, there are no Pre-Columbian nephrite jade artifacts found in this culture region. The jade of Pre-Columbian Mesoamerica is exclusively jadeite jade.

Jadeite (NaAlSi2O6) is a relatively rare, monoclinic pyroxene with subvitreous to vitreous luster, that is translucent to opaque, and occurs in every color except red (pure jadeite is white). The greens of jadeite are due to iron or chromium substitution for aluminum where iron produces the shades of earthy green and where chromium produces the electric, emerald green of "Imperial" jade. Jadeite forms a solid solution series with the jadeite-related minerals acmite, diopside, and cosmochlor; therefore, jadeite mineralogy is extremely complicated and beyond the scope of this paper.

Jadeite is the mineral, jadeitite (not misspelled) is the monominerallic rock formed entirely of the mineral jadeite. Jadeite is a rare mineral and jadeitite is an even rarer rock. It is a blueschist facies metamorphic rock that forms under 5 to 7 kbars of pressure at temperatures of from 200o to 400oC (Mason and Berry 1968). Although there are probably no more than 6 geologic deposits of jadeitite rock in the world, gem-quality jadeite jade is only found in Burma which is the sole source of "Imperial" Jade. Jadeite jade from other sources, including Guatemala, are not considered by gemologists to be pretty enough to be used in jewelry. The prehistoric cultures of Burma and Pre-Columbian Mesoamerican used jadeite jade; however, Burmese jadeite jade was not imported into China until Ming Dynasty times, a late date with respect to the depth of Chinese history.

Many jade substitutes exist that are considered by archaeologists to be "social" jades; that is, greenstones that were used along with nephrite or jadeite jade. In gemology, these are considered to be pseudo-jades or jade substitutes. Greenstones used in place of true jade and their gemological names include:

Albite - Albitic Jade
Aventurine - Indian Jade
Chrysoprase - Australian Jade
Green Grossular Garnet - Transvaal Jade
Malachite - African Jade
Serpentine - New Jade, Korean Jade, Jaguar Jade
Talc (soapstone, steatite) - Sochow Jade
Green Vesuvianite - American Jade

In summary, there is no exact meaning to the term "jade" in geology and it means different things to different people in different cultures, past and present. The term "jade" is a generic term that can be used to describe a wide range of greenstones that are attractive enough to be fashioned into ornaments and decorative objects like statuettes. The terms "nephrite" and "jadeite" do have exact meanings and should only be used when the artifacts, ornaments, or objects of art are composed of felted, micro-crystalline tremolite-ferroactinolite or jadeitite, respectfully.

Anderson, B.W., 1976, Gemstones for Everyman, Faber and Faber, London, Eng., 368 p.

Bishop, R.L., and Lange, F.W., 1993, Sources of Maya and Central American Jadeitites, in Precolumbian Jade: New Geological and Cultural Interpretations, ed. Lange, F.W., University of Utah Press, Salt Lake City, p. 125-130

Desautels, P.E., 1971, The Gem Kingdom, Random House, Inc., N.Y.C., N.Y., 252 p.

Diaz del Castillo, B., 1568 (1632), The True History of the Conquest of Mexico, Ann Arbor University Microfilms, Inc., Ann Arbor, Mich., 515 p. (translation: Keatinge, M., 1800, reprint 1966)

Dunning, A.B., 1960, Lithic Factors Affecting Selection for Tools, Jour. of Alabama Archaeology, vol. 6, no. 2, p. 65-70.

Emmons, G. T., 1923, Jade in British Columbia and Alaska, and Its Use by the Natives, in Indian Notes and Monographs, No. 35, ed. Hodge, F.W., Museum of the American Indian, Heye Foundation, N.Y.C., N.Y.

Foshag, W.F., 1957, Mineralogical Studies on Guatemalan Jade, Smithsonian Miscellaneous Collections, vol. 135, no. 5, 64 p.

Garza-Valdes, L.A., 1993, Mesoamerican Jade: Surface Changes Caused by Natural Weathering, in Precolumbian Jade: New Geological and Cultural Interpretations, ed. Lange, F.W., University of Utah Press, Salt Lake City, p. 125-130

Gay, C.T.E., 1967, Mezcala Stone Sculpture, The Human Form, The Museum of Primitive Art, Studies No. 5, N.Y. Graphic Society, greenwich, N.Y., 39 p.

Griffin, G.G., 1987, Formative Guerrero and its Jade, unpublished manuscript, 10 p.

Harlow, G.E., 1993, Middle American Jade: Geologic and Petrologic Perspectives on Variability and Source, in Precolumbian Jade: New Geological and Cultural Interpretations, ed. Lange, F.W., University of Utah Press, Salt Lake City, p. 9-29

Hauff, P.L., 1993, The Enigma of Jade, with Mineralogical Reference to Central American Source Materials, in Precolumbian Jade: New Geological and Cultural Interpretations, ed. Lange, F.W., University of Utah Press,
Salt Lake City, p. 82-103

Lange, F.W., 1993, Introduction, in Precolumbian Jade: New Geological and Cultural Interpretations, ed. Lange, F.W., University of Utah Press, Salt Lake City, p. 1-6

Moriarty III, J.R., 1973, Aztec Jade, Lapidary Journal, Vol. 26, No. 10, p. 1428-1433, and 1440

Peterson, F.A., 1959, Ancient Mexico, An Introduction to the Pre-Hispanic Cultures, G.P. Putman's Sons, N.Y.C., N.Y., 313 p.

Rossman, G.R., 1974, Lavender Jade: The Optical Spectrum of Fe3+ and Fe2+ - Fe3+ Intervalence Charge Transfer in Jadeite from Burma, American Mineralogist, vol. 59, p. 868-870

Schumann, W., 1997, Gemstones of the World, Sterling Pub. Co., Inc., N.Y.C., N.Y., 271 p.

Sinkankas, J., 1959, Gemstones of North America, D. Van Norstrand Co., Inc., Princeton, N.J., 675 p.

Strack, E., 1972, Jade - Stone of Heaven, Lapidary Journal, Vol.26, No.7, p. 1084-1094

Woodward, L.L., 1987, Jade Industry in Guatemala: Old and New, Viva Mag., vol. 3, no. 1, 4 p. (reprint)


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* Daniel G. Gall, Ph.D. * P.O. Box 306 *
* 502 North Chestnut Street * Mount Olive *
* North Carolina * USA * 28365 *