Is it a true nephrite (actinolite-tremolite) rock? You ask the The
$64,000 question, Derek.
Jade in Gastown Vancouver and next-door Chinatown is never labelled
with any details which would help the buyer to know. I recommended
labelling with these details but not defining jade as definitions
vary so greatly. Details based on objective scientific facts can be
verified and it is then an explicit fraud to falsify them. Polar
jade is sold in the gift shop district which also sells Whistler
black jade and a white jade of unknown origin etc. What I have put
out for discussion is: What would be helpful on the labels?
One answer I got was that three GIA measures of H, SG and spot RI
might work. Leonid has pretty well convinced me that this would at
least be a good start. It does not have to be 100% definitive to be
helpful. So let’s say you are wondering (as you posted) if the piece
you might buy is a true nephrite-actinolite rock.
The H is given on the label as being in the jade range. The SG is
also right (around 3) and then what about spot RI? I have never done
a spot RI test so this still puzzles me. I do know that bona fide
jade I got from a jeweller whose credentials are not disputed is less
10% actinolite-tremolite as the assay proves. So let’s say Leonid
does a spot RI test on it. The >90% fraction must contain a lot of
minerals other than actinolite-tremolite. The H is just one value.
The SG is just one value. The spot RI will be a number of values will
it not? And even if you do other optical crystallography tests like
those with polarized light (birefringence) or X-ray spectography the
complex nature of the rock will cause them to also have multiple
values. Maybe somebody has an answer to this problem.