There are many jade items sold on ebay but sometimes it is difficult to tell if they are made of real jades. Only jadeite and nephrite are usually considered as real jades. Jadeite has a density of 3.32 - 3.33 while that of nephrite is 2.98 - 3.10 with an average of 3.04 It is generally easy to tell jadeite by performing a hardness test (see my other guide for scratch test) but it is extremely difficult to tell nephrite by performing the hardness test alone. Therefore in order to distinguish items made of real jade from that made of other stones, I had performed the density test on sixty-nine ebay jade items.
Density of an item is calculated by dividing its mass (weight in gram) by its volume (cc or ml). Therefore the density test is performed as follow:
Purpose: Using the density test to identify jadeite and nephrite items (jadeite: 3.20-3.33; nephrite - 2.98 - 3.33)
Equipments: Pesola spring scales - 100 gram Microline scale; 500 gram Light Line scale; 2500 gram Medio Line scale. (The Swiss made Pesola spring scales are the best in the market. The Microline is better but more expensive than the Light Line and has two years' warranty instead of one year's warranty. The only authorized U.S. dealer for Pesola spring scales is Forestry Suppliers, Inc. I selected the above three volumes because the 64 items I tested ranged from 20 gram to 2500 grams. If you have jade items greater than 2500 grams, then you need to get the 5000 gram and 10000 gram spring scales and they are quite expensive. However, the accuracy of these Pesola spring scales are truly amazing, I used both 100 and 500 gram spring scales to weigh the items and then weigh them again on two electronic scales (one is a Mettler scale which is very accurate). For items that are 100 grams or less, they are identical; for items between 101 and 500, they are within 1 to 2 grams. Therefore, they are real worth of the money. I did a lot of researches before I settle on this spring scale. I had never heard of Pesola before this.
Buckets of water (one small, one large); strings, pony tail holder, rubber bands, paper towel (to dry items)
(1) Make sure each bucket is wide and deep enough for you to dip the tested jade item inside. The reason you need two buckets is you need a small one for items that are generally smaller (weight less than 400 gram) and one that is big enough for bigger items.
(2) Use the Pesola 100 gram spring scale to measure any items that weigh less than 100 grams and use the 500 gram spring scale for items between 101 gram to 500 gram. Use the 2500 gram spring scale for items that weight more than 500 grams but less than 2500 grams. If you have an electronic scale or a big spring scale to preweigh the items it will be helpful in deciding which spring scale to use. Please bear in mind 1 kg (1000 gram) is equal to 2.2 lb or 448 grams equal 1 lb.
(3) Both the Pesola 100 gram and 500 gram spring scales have crocodile clamps come with them. You can just use the clamp to grasp the tested jade item. Hold the spring scale by its top handle. Record weight of the jade item in air. Then slowly immerse the whole jade item completely into the water bucket and record its weight in water. It is okay for the cramp to touch the water and it should not affect the water weight that much. Some time some jade items cannot be grasped with the scale clamps and then is when I found a piece of string, a rubber band or a pony tail holder (the best) come in quite handy. I use one of the above to wrap around the piece before I weigh them. Since I weigh the extra piece of string in both air and in water, it will cancel out at the end. I also find the use of a piece of tapes to tape some of these items and then use the clamp to hold them quite helpful. The string method worked very well with a lot of Hongshan pieces bcause I can just put the string through the chi holes. The 2500 gram spring scale comes with a strong hook. Wrap the big items with strong strings or use a net to wrap the item and then hook it with the 2500 scale. Follow the same procedure to weigh the item.
(4) To calculate the volume of the jade item:
Volume of jade item (in gram) = Its weight in Air (gram) - its weight in water (gram)
To calculate the density of the jade item:
Density of jade item = Weight of item in Air/Volume of Item
Example: The weight of an Hongshan piece in Air = 515 gram
Its weight in water = 350 gram Its volume = 515 - 350 = 165
Its density = 515/165 = 3.121
If this peice can also pass the hardness test, then more than likely this piece is made of nephrite
I have tested 69 jade items. Three are know jadeite items from two ebay dealers and I obtained a density from 3.200 to 3.300. All thre had no problems in passing the hardness test. I tested two pieces of known nephrite rocks from an ebay dealer and obtained density of 2.833 and 3.000. I obtained five pieces of nephrite with different colors from a Texas rock company directly and obtained density: 2.929 to 3.083 for 3 green nephrite rocks; 2.725 for a black nephrite and 2.960 for a pink nephrite. I tested over fifty jade items from three ebay dealers: 39 jade items have density below 2.980 and 15 items are above 2.980. The lowest is 2.529 and the highest is 3.121 Many Hongshan pieces actually have densities around 2.90 -3.00 but their color and texture just do not look like typical nephrite. Suprisingly the darker jade items and the one with white patina are actually made of nephrite (they also passed the hardness test). I only tested one zong and it failed the density test. Therefore, I believe any jade item that have a density of at least 3.000 and pass the hardness test, then it is very likely that they may be made of nephrite. The one that have density around 2.900 - 3.000 will be inconclusive and require some more studies. Also please bear in mind that many authentic and ancient Chinese jade items were actually not made of either jadeidte or nephrite.
Other test results: (density)
Agate - 2.500 - 2.600
Black Obsidian Rock - 2.417
Red calcite - 2.646
If you have any further questions, feel free to contact me through ebay. Than you.