If you have something that is actually valuable you would be
foolish to trust anyone who is not an expert.
First I'll wholeheartedly agree with Richard, above. And since you
ask the question I'll guess that you need an expert appraisal, also
since it's a whole collection. Just for your own purposes - I want
to stress that I'm not saying you should appraise the lot yourself -
even fine jade has a waxy luster. Well polished quartz can and might
look like glass. Jade will have something of a look of finely
polished wood that's hard to describe or explain. It's the eye that
can see the difference that's the expert. For many other jade
substitutes there is a simple test that you CAN do yourself.
Somebody showed me a "jade" figurine and said that Sotheby's had
ID'd it as real jade. I took one look, literally said, "They're full
of &%^" and pulled out my pocket knife. Sure enough, the blade bit
into the stone immediately. With both jade and quartz the blade will
skip across the stone like it's ice. Most of the jade substitutes are
easily scratched, and you don't have to scratch them - if the blade
wants to dig in, it's not jade.
If it's really a large lot, you need a pro. If it's a large, fine
lot and you have pics, I have a friend who might be interested - if
so you can email me.....John D.