Every jade dealer worth his salt will be able to tell you the rough stone that he is holding is a Jadeite Jade or not, just by hefting the stone.
Most of us have seen it in the movies that a professional gunman or a seasoned police officer who handles guns often will be able to know the number of bullets left in the magazine plus the one in the chamber by the heft of the gun. Heft here simply means that one ‘weighs’ the object using his palm or fingers.
The heft of a stone is related to the specific gravity of the stone, that is, the relative weight of the stone in comparison with an equal amount volume of water.
I was based in Yangon, Myanmar (Burma) for many years as a hotelier. It was in Yangon that I learnt the jade trade under many Burmese jade dealers, gemologists and jade cutters. And the first lesson was to heft the stone.
Day in day out, one has to practice hefting a variety of rough stones until you are so good that you can separate the wheat from the chaff or differentiating jadeite jade from other gemstones even when you are blindfolded.
A close Burmese friend of mine who was the ex-Director of the Myanmar Gems Emporium taught me a few valuable lessons. He gave me some rough jadeite jade and some cut and whole polished ones too. These few stones were to serve as my bench-mark parameters.
The first thing I woke up in the morning was to heft these few stones and the last thing I did before I went to bed was to heft these few stones. And in between the day, I was to ‘play play’ with these few jadeite jade stones. During the day, in my fussy head there was only jade, jade and jade. During the night, I kept dreaming about jade, jade and jade. It was a very focused exercise. When I was separating the various stones, I kept chanting my jade mantra, “this is jadeite, this is not jadeite, this is jadeite, this is jadeite.” Until it was so ingrained in me that upon a stone being placed in my palm, I could tell you that this was a jadeite or this was not a jadeite.
Then he gave me some other stones like rough quartz, petrified wood, lapis lazuli, agate and other gemstones commonly found in Burma for hefting practice. Some of these you could sight-id them that there were definitely not jade by the outer layer of crust. But some other stones like serpentine, nephrite, chrysoprase and other granite boulders have the same outer surface characteristics as jadeite.
One day he brought me a bag of mixed rough dark green stones with no open windows (that is the crust of the stone is still intact) and he let me have a glance over. Then I was blind-folded and was asked to separate them into jadeite jade and other stones. Ha ha, just like some Hong Kong King of Gamblers kick-ass movies where you closed your eyes and used your thumb and index finger to tell the card of a Mah-jong tile and you must be right 100% of the time.
Well, I did not get it right the first few times. After many months of practice it was easy game. So given a pile of stones I could pick up jadeite jade with ease.
Now when you heft a small stone it is better to use your 4 fingers, bounce the stone slightly and let it fall onto your fingers under gravity. Your fingers are much more sensitive than your palm and you are more likely to get better and better results. With a large boulder, say 5 or 6 kg use your whole palm. Smaller gemstones below 5 ct (or 1gm) may need a lot of practice but you will get the feel.
So keep hefting jadeite jade daily and you will be as good too.
By the way, just to preen my feathers a bit, I am blady good at separating good Old US of A $100 dollar bill from the counterfeit. Back in early 90s when I was in Phnom Penh, Cambodia, counterfeit $100 dollars were common as there was little law and order in a country just recovered from the purges of the Khmer Rouge. And we used to count US dollars by the thousands daily.
As I counted a 100 piece bundle of US$100 notes I could pull a counterfeit out by the feel of the texture on my thumb and fingers. I have done it many times. Really it is no big deal, a lot of people can do that too.
Practice, practice and practice, that should be your mantra if you are passionate in learning the ropes of a subject.