Jade Identification
Undoubtedly, the quickest and easiest of the reliable determinations is using a petro-graphic microscope, or a refractometer, to determine the refractive index. A trained micro-scopist can very rapidly differentiate between the varieties of jadeite, between jadeite and nephrite, and between jade and many of the jade-like minerals. Best of all, it takes only a few tiny grains of material, which can be removed easily from some inconspicuous place on a carving. The major drawback is that it requires an operator trained in the techniques of optical crystallography, as well as an expensive piece of equipment.
The most precise jade identification involves the X-ray diffraction powder method. This, too, requires only a very tiny amount of sample. A narrow X-ray beam is passed through the powdered mineral, which diffracts it into a pattern of lines. The pattern is recorded on photographic film, which can then be compared with a standard file of films containing patterns of known nephrite, jadeite, and other minerals. This kind of identification is fundamental because it depends on the fact that every crystalline mineral yields a characteristic pattern stemming from differences in internal structure. More info for diamond rings can be find here 1ct diamond engagement ring
A quick survey of obvious and not-so-obvious jade substitutes—many used innocently and with no intention of fraud—shows the magnitude of the identification problem. Only a very few substances are difficult to distinguish from jade. Jade-like glass, plastics, soapstone, and softer varieties of serpentine are easily separated from true jades because they are scratched readily by a good penknife. Jade carvings from ancient tombs will also scratch because their surfaces have become softened through centuries of exposure to the chemicals of decomposing bodies and soil solutions. Very old, archaic jade pieces may suffer the same alteration. If there is any doubt about these, they are worth an X-ray determination of the powdery surface material, which will show that they are still nephrite. Since jadeite was unknown in China until relatively modern times, all the ancient and altered jade will be nephrite.
Of the harder jade substitutes, the most troublesome to identify are bowenite; a green, fine-grained variety of idocrase known as cali-fornite; some fine-grained pieces of zoisite and diopside, and a few other related silicate minerals. For some, a determination of specific gravity is sufficient evidence. This, coupled with a reading of refractive index, is usually enough. Except in obvious cases, these silicate minerals are best left to trained mineralogists and gemologists for proper identification.
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