how to tell real jade?

Question

can you tell me if you take a piece of jade and wrap it with a piece of human hair - and try to "burn" the hair with a flame and it does not burn - does that mean it is real jade? A person in a store in China did this in front of us - told us it is real jade...Thanks

Answer 1

The name “jade” refers to two different stones, nephrite and jadeite, which have similar properties. Nephrite, the jade carved in China for thousands of years, is a calcium magnesium silicate with hardness of 6 to 6.5 on the Mohs scale (slightly softer than quartz). Although not especially hard, nephrite’s structure of tightly packed microscopic fibers makes it uniquely tough. In fact, it is the toughest (hardest to break) of all stones, which makes it the perfect material for delicate carvings. Translucent to opaque, nephrite’s subdued colors include creamy white, celadon, spinach, russet, and yellow.

Jadeite (fei cui in Chinese) is a sodium aluminum silicate, slightly harder to scratch and a bit less tough than nephrite. Jadeite’s colors are more vivid and include green, white, russet, black, and a delicate lavender.

Nephrite’s combination of moderate hardness and extreme toughness makes it difficult and tedious to carve. This was all the more true for carvers long ago, who worked solely by laborious abrasive grinding using foot-powered treadle lathes. Although nephrite is not all that rare in the common colors and grades, there is a strong temptation to foist a cheaper, easier-to-carve pseudojade onto the unwary buyer. These lesser hardstones are sometimes offered, dishonestly, as “a type of jade.” So when buying jade, first assure yourself that what you are buying really is jade.

Nephrite’s imitators include serpentine, bowenite, white chalcedony, aventurine, and even Peking glass. These are often sold with deceptive names, such as Honan Jade, Soochow Jade, or New Jade for serpentine. Without becoming a mineralogist, how can the collector tell jade from pseudojade? First, of course, is to see and handle as much true jade as possible. Jade, especially, is a tactile material. There is even a story of the famous blind jade dealer A. J. Gump (of Gump’s in San Francisco) being able to judge jade solely by the touch of his fingertips. So begin by learning what jade looks like and feels like. Books, museums, and friends’ collections can prove educational.

A visual inspection can reveal much. Jade’s translucence lets you see slightly below the surface, creating a visual effect quite unlike most of its imitators. Older jades that were polished using soft abrasives will often reveal a slight “orange peel” effect on the surface. And although true jade comes in a range of colors, it will probably not show the sickly yellow-green of certain serpentines or the dull, opaque white of many chalcedonies.

Jade’s hardness can provide another quick test. The sharp point of a steel pen-knife blade, which is just under 6 in hardness, should not be able to nick or scratch the material. This test should of course be done with great care and with the owner’s permission. Choose a polished, hidden portion and press hard. Remember that you need only make the tiniest (1/32”) nick, or even just feel the bite of the point into the stone to determine that the hardness is less than 6. In that case, the material is likely a softer pseudojade such as serpentine or even soapstone. A word of warning about “scratch tests”: bowenite (a hard variety of serpentine) will sometimes “pass” the test if it is not done properly. Chalcedony (a form of quartz), being actually harder than jade, will always pass the test. Fortunately, chalcedony imitations are not as common as those in softer pseudojades. And of course, true archaic jades that have undergone millennia of surface degradation cannot be tested this way.

A more definitive test is to measure the material’s specific gravity. Specific gravity is a measure of density—in other words, the ratio of the item’s weight to what an equal volume of water would weigh. For a simple shape, such as a cube or sphere, specific gravity can simply be calculated as weight divided by volume. But for the typical jade carving, the “hydrostatic” method is more practical. Invented by Archimedes over 2000 years ago, this involves weighing the item in air and then again while it is fully submerged in water. A beam-balance is often used, with the test item suspended in water from a thread beneath the balance. The specific gravity (SG) is then

SG = (weight in air) / (weight in air - weight in water).

Nephrite (SG = 2.90 - 3.00) and jadeite (SG 3.33) can be readily distinguished this way from most pseudojades, which are typically 10% or so lighter. In fact, after some years of handling jades, one can learn to tell jade from pseudojade simply from the “heft” of the piece in the hand.

Some very deceptive jade imitations have been made from glass, particularly the dense, opaque variety known as Peking Glass. Glass reveals itself, under a 10x lens, by its tiny swirls and bubbles.

Answer 2

How To Tell Real Jade

Answer 3

...I'd still go to a reputable jewler and get it verified. There are many kinds of stone that were traditionally considered "jade" in China, so long as they were green. These days it's a bit more regulated.

Answer 4

There are different tests of authenticity of jade, because there are a few minerals belonging to the jade group--
--for more details please consult the sources below.
Good luck.

Answer 5

Use other minerals and test the theory