Fine green jadeite can command exceptional prices. Christies auctioneers have sold jade jewelry for millions of dollars. When investing this sort of money in jewelry it is essential to know that you are buying the real thing.
A better question would be: "Is this real jadeite?" This is a different approach to the possibility of being swindled. First you worry about whether the piece offered is actually jadeite, before worrying about dying or staining to enhance its value.
A likely scenario is you are browsing market stalls of jewelry in S.E. Asia or Central America and wondering whether to spend $50 or more, on that nice jade ring which fits so comfortably, or a jade pendant, but is it real jade and has it been dyed? Today it is reported that most of the Asian trade is with jade that has been "color-enhanced" in some way.
Within this scenario, is there some simple way of telling the difference between real jade and an imitation, dyed or otherwise? Yes, there is, but the vendor probably wouldn’t let you do any tests because he wants to make a sale. But does this uncertainty really matter all that much, if you like the piece of jewelry and price is not excessive? This is the mass market, or fun tourist trade which is always "caveat emptor".
There is plenty attractive dark green jadeite jewelry that you can buy very cheaply in the shops and from street vendors in Antigua Guatemala, a lovely tourist town in the Western Highlands. It is genuine untreated jadeite for reason that such opaque material is not amenable to dyeing. Some high quality translucent green, lavender, blue and yellow jadeite is found in Guatemala.
If authenticity is important to you then you buy jade items, be it carvings, jewelry or cabochons etc. from reputable dealers who fully describe what they are selling and provide a "Certificate of Authenticity", on request, done by qualified gemologists.
"Hong Kong" jadeite pieces are categorized A, B, and C according to prior treatment. Type A is untreated jadeite showing its natural color, except for a waxing and polish, like you may do to spruce up your furniture. Translucent A type jadeite of good color and quality is rare and expensive.
Types B and C jadeite have been treated to enhance their color, such as by a bleaching process involving a strong acid leach, followed by impregnation with a polymer, probably polystyrene. Type C, after leaching, or heating, is stained with dye to imitate bright greens or pinks mainly. Most dyes will come off if the piece is rubbed with a swab moistened with solvent, like acetone. Microscopic examination may reveal irregular staining concentrated along grain boundaries. Jadeite is not porous like chalcedony, so it is difficult to satisfactorily dye, or stain, particularly in a color shade typical of valuable natural jadeite. Dyed jadeite is said to appear red through the Chelsea filter, and dyed lavender material to fluoresce orange with SW UV.
What is confusing is that the term "jade" includes two minerals of different composition and properties viz., nephrite, an amphibole mineral, Ca2 (Mg,Fe)5 (OH)2 [Si 8O22] ideally, in the tremolite-actinolite series, whereas jadeite is a pyroxene mineral, NaAl [Si2O6] ideally. Nephrite jade is by far the most common and is found worldwide whereas jadeite has a more limited occurrence, notably from Burma, Japan, Kazakhstan, Celebes, California, Mexico and Guatemala, with present day production coming mainly from Burma and Guatemala. Jadeite cutting centers are in Hong Kong and Taiwan, and in Antigua, Guatemala.
Nephrite is composed of a fibrous felted crystals which result in an extremely tough material. Jadeite is composed of minute interlocking granular crystals, like a quartzite, which is tough too, but is more easily broken than nephrite; a geological hammer test is more applicable to a stray pebble found on a river bed. Nephrite has a hardness of 6 to 6.5, hence is scratched by quartz (7), but jadeite is slightly harder at 6.5 to 7, in fact you can scratch nephrite with a sharp edge of jadeite. A steel knife (5.5) scratches neither. It is helpful to have samples of rough and polished jadeite and nephrite on hand to compare the subtle differences.
Jadeite is slightly heavier than nephrite and has a higher refractive index (Jadeite SG 3.3 to 3.5, RI 1.66 whereas Nephrite has SG 2.96 to 3.10, RI 1.62). Small gem material can be tested in the heavy liquid methylene iodide (SG 3.3) in which jadeite will sink and nephrite float.
Specific gravity measurements may easily be done on carvings and loose samples. It is a sure way of identifying jadeite from the many attractive green simulants, which include nephrite, idocrase, hydrogrossular (Transvaal jade), bowenite, chrysoprase, aventurine, prehnite and glass. It is not possible to measure SG for items mounted in jewelry.
There are two ways the physical properties of jadeite may vary. The chemical composition can vary by "solid solution" with other pyroxene minerals, particularly diopside and acmite, i.e., Ca, Mg and Fe, Mn substitute for Na and Al in the structure. Secondly, jadeite, pure or otherwise, may be mixed with other minerals, particularly the feldspar albite, and be more like a rock. Some Guatemalan dark green jadeite contains white albite giving it a mottled effect, and although attractive, this causes undercutting on polishing, and can lower the specific gravity as a whole.
The color and transparency range of jadeite is much more extensive than that of nephrite jade. Nephrite is typically opaque green of various shades, dull to bright, and changing to light green and yellows towards the outer oxidized portions of a boulder. A white "mutton-fat" jade variety is low in iron content, being essentially tremolite, and a black opaque variety is not uncommon..
In contrast, jadeite, particularly the Burmese (= Chinese) variety can be very translucent in a wide range of colors including greens, (emerald-green and blue-green), yellow, orange, red, pink, lilac, blue, mauve, black, charcoal, white, cream, white with green sploches.
The "Imperial Jade" or emerald-like jadeite is colored mainly by a trace of chromium. By transmitted light it shows an emerald-like absorption spectrum but more diffuse, with lines in the red at 691, 655 and 630 nm. which serve to distinguish it from dyed material having only "woolly" bands in the red. Also an Fe? band in the violet at 437 nm is best seen in paler varieties of green and lavender (3). The pink color is thought to be caused by traces of manganese. The bright and delicate colors are found in jadeite lacking in iron, it being less than 0.5%. Dyed or stained jadeite colors try to imitate the highly desired emerald green and lavender varieties.
In conclusion, firstly one must make sure the stone is in fact jadeite and not one of the many simulants. Then if it is jadeite, is the color natural, or is it due to chemical treatment? Jade dealers would know and so too would gemologists at a gem testing laboratory. The causal buyer of jade may not know, but if appreciable money is involved on the outcome it is sensible to get the item tested by a reputable organization, such as the Hong Kong Jewellery and Jade Manufacturers Association (HKJJA) or other GIA type organization.