synthetic corundum.7, synthetic ruby, hydrothermal, gems

jade, nephrite, USA, California, gems

Diamonds are said to be forever, but there are very few gemstone materials about which there has developed throughout the ages such a curious lore as there has about jade. In California, this lore has attracted statewide attention, principally because deposits containing the jade minerals, jadeite and nephrite, occur at several places throughout the state and because gem or lapidary quality jade has been recovered in substantial amounts from several of these localities. Many dense, fine-grained, green-colored rocks have mistakenly been called jade; but, from a gemological point of view, jade is a name given to the massive, gem-quality varieties of the two rock-forming minerals nephrite and jadeite. Nephrite is an amphibole, a silicate of calcium and magnesium that usually contains a small amount of iron. Jadeite, on the other hand, is a pyroxene and is a silicate of sodium and aluminum; usually, however, it contains variable amounts of two other pyroxene minerals, diopside (silicate of calcium and magnesium) and acmite (silicate of sodium and iron), which, when present in sufficient amounts, produce a dark green variety of jade called chloromelanite. It is true that nephrite and jadeite resemble each other very closely, but they can be distinguished by their different physical and chemical properties. Not only is jadeite harder than nephrite but it has a higher specific gravity. In general, the specific gravity of jadeite is 3.32 and that of nephrite is 2.98. Both of these minerals have a wide range of colors and color shades. Jade ranges in color from pure white, through every possible shade of green to amethyst, mauve, violet and light blue, yellow, orange and diverse tints of brown, red, and black. Because the colors in nephrite and jadeite usually are distributed unevenly, descriptive terms such as mutton fat, spinach green, and onion green have been employed to describe jade. Successful use of jadeite or nephrite as gem quality jade depends upon several important properties, such as desirable color, color pattern, and a certain degree of translucency. Because of this, the amount of jadeite and nephrite that is of gem quality is rather small in comparison to the amounts of these materials that are of mineralogical significance only. The occurrences of nephrite and jadeite, especially nephrite, are comparatively widespread and common in California. Most deposits of these interesting gemstone materials have been found only in or adjacent to bodies of serpentine, an association that seems to be characteristic of nephrite and jadeite occurrences throughout the world. Exceptions to this, however, are the unusual occurrences of nephrite associated with magnetite, epidote, chlorite and garnet in irregular contact metamorphic zones between granitic rocks and dolomitic limestone, near Victorville in San Bernardino County and in the western part of the Eagle Mountains in Riverside County. Many of the occurrences of nephrite and jadeite in California are well known to individuals and groups of amateur mineralogists but the several reports that follow, which have been prepared and published by the Division of Mines and Geology, describe in detail a few of the best known and most significant occurrences of nephrite and jadeite in California.

gems, jade, jadeite, fei cui, Mesoamerica, Mexico, Guatemala, Costa Rica, Mayans, Olmecs, Aztecs, archaeology, history, archaeogemology, Pre-Columbian jade; Costa Rica; Maya; exchange; iconography, lapidary

The Jaguar’s Children: Pre-Classic Central Mexico has as its subject one of the most arresting topics of New World prehistory. The Olmec of Mexico—originators of the earliest great civilization in Middle America—produced an extraordinary art. Its impact on contemporary and subsequent Mexican developments was enormous. It is this impact on an area in the Central Highlands, parts of the states of Morelos, Puebla, and the Valley of Mexico, that is described here by Michael D. Coe of Yale University. Long a student of the Olmec era, Dr. Coe discusses the extensive site of Tlatilco, the transitional site of Tlapacoya, and the very important and previously unpublished site of Las Bocas. Problems of symbolism, iconography, and the close relation of Olmec art to religion are examined, as well as the relation of Olmec culture to that of Central Highland tradition. Illustrated by over 200 pieces, many published for the first time, the emphasis has been placed on material from Las Bocas. The most important “baby-face” figures of the period have come from that site. These are graphic and humanized representations of the major Olmec deity, a rain god whose shape was that of a were-jaguar, a fat, childlike creature with feline features. Believed to have been born of a jaguar father and a human mother, they are the Jaguar’s Children. Dr. Coe first published on Pre-Classic Middle America and the Olmec in 1957 and is the author of the important articles on them in the Handbook of Middle American Indians. His excavations at the early village site of La Victoria on the Pacific coast of Guatemala were reported in the Papers of the Peabody Museum of Archaeology and Ethnology, Harvard University (1961). He wrote the volume on Mexico (1962) in Praeger’s Ancient Peoples and Places series and was engaged in a work on the Maya to appear in the same series.

gems, jade, fei cui, pyroxene jade, jadeite, amphibole jade, nephrite, dyed nephrite, dyed jade, dyed nephrite

Since we first encountered dyed jadeite in 1956, we have expected the appearance of dyed nephrite, but until recently we had not seen or heard of any. Figure 13 is a photograph of a well-carved nephrite tablet with chrome-green mottling. Spectroscopic examination of the green areas proved to us that the color is due to dye. Possibly, nephrite does not take the dye uniformly; therefore, this accounts for the absence of dyed material in the trade.

gems, gem testing, gemology, specific gravity, scales, weights, weighing

This unique survey of the history of weighting and its instruments, from the earliest known examples in the millennia before Christ to the modern era, is generously illustrated with 98 plates depicting scales, weights, and containers from the great collections of the world. It includes the known hallmarks of the scale and weight makers of Western Europe and lists of the weights of the world and their metric equivalents, by country and by name of weight. [RWH: Like most Western works, this book completely ignores the tremendous work done by Arabic-language scholars like al-Bīrūnī and al-Khazinī, who were measuring specific gravity hundreds of years before European scholars.]

jade, nephrite, treatments, dyed jade, gems

Burma, jade, gems

Burma, jade, gems

Describes maw-sit-sit, a distinctive bright to dark green ornamental rock from northern Burma (Myanmar), occurring near the jadeite deposits of the Hpakan region. Gübelin examines its appearance, gemological properties, texture and mineralogical composition, distinguishing it from jadeite jade and other green ornamental materials. The material is characterized by an intimate mixture of contrasting green and dark minerals that produces its characteristic mottled appearance. Microscopic and mineralogical observations demonstrate that maw-sit-sit is not a single mineral but a complex rock composed of several constituents. The article documents its occurrence, properties and identification and represents one of the earliest detailed gemological descriptions of this unusual Burmese gem material. Also contains brief mention of the Naniazeik ruby/spinel mines.

gems, jade, jadeite, fei cui, Mesoamerica, Mexico, Guatemala, Costa Rica, Mayans, Olmecs, Aztecs, archaeology, history, archaeogemology

Jade, the most valued of all Maya products, is very scarce or does not occur in the Yucatán Peninsula. Foshag (1955, p. 11), in listing seven varieties of jade found in archaeological collections from Middle America, notes the intimate association of jade in situ with serpentine deposits and points out that they normally have an enveloping skin of albite in the process of conversion into jade. He observes that where there are deposits of serpentine there is a good possibility of finding jade, and lists the following known deposits: the Sierra de las Minas north of the middle Motagua, with an outlying spur south of San Agustín Acasaguastlán; the Sierra de Santa Cruz northwest of Lake Izabal; the Sierra de Chuacús in northern El Quiché north of the Río Negro and extending into adjacent Baja Verapaz; and a small area north of Huehuetenango. More recently, jade was actually found in situ near Manzanal in the Sierra de las Minas (Foshag and Leslie, 1955). Small deposits of serpentine are situated, according to Sapper, near Chimalapa in southern Chiapas, close to the Guatemala border. Of these areas—and it must be remembered that, except for Manzanal, jade had not been found anywhere; the rest were only potential sources—only the Sierra de Santa Cruz and perhaps the northeastern end of the Sierra de las Minas are in lowland territory. Whether there is jade in these two areas, and whether the Manche Chol who inhabited the region (they were called Toqueguas there but were of Chol speech) worked it if it existed there, are uncertainties. Pusilhá and Lubaantun, which were in Chol territory at the time of the Spanish conquest, have not shown much evidence of jade wealth, and the same is true of Quiriguá, which lies in territory probably occupied by the Chol in the sixteenth century. On the other hand, the relatively insignificant sites of Pomoná, Kendall, Camp 6, and the not very important Mountain Cow, to the east and west of the Maya Mountains in British Honduras, have yielded some very fine worked jades in the course of quite minor excavations. One is led to speculate whether there could be jade in that range.

gems, jade, pyroxene jade, fei cui, jadeite, dyed jade, treated jade, composite jade, plastic-coated jade

We have commented on the variable fastness of the colors used in dyeing jadeite. We recently tested some dyed stones of excellent color. The owner stated that he had purchased them in 1955—a full year before we first encountered the stones in the course of our testing work. He further stated that to his recollection they had not faded. In another note, a necklace of round jade beads showed the treated spectrum and the normal jadeite absorption line at approximately 4370 Å, but the refractive index was approximately 1.55 by the spot method. Magnification revealed that the stones were plastic coated, in addition to being dyed; hence, the “wrong” refractive index for jadeite. And another note: Figure 3 illustrates a small, flat, oval cabochon of jadeite, one of a group that a manufacturer stated had altered radically in appearance following normal steam cleaning of finished jewelry. What had originally been evenly colored medium-green stones became mottled with numerous white, intersecting cracks. The only suggestion we could offer was that perhaps the stones had been oiled to camouflage the cracks before they reached the manufacturer.