There have been many discussions about the effect of heat treatment
on the color of stones and I was left wondering - Does jade change
color when heated?
I have no shortage of low grade nephrite jade as at
http://www.ganoksin.com/gnkurl/18i
So I kiln fired some with very nice results - greenish-black turns
become light orangey-brown to bright reddish-orange. I hope to have
more time this summer so that I can get more systematic about this
and also I want to try out some jade saw dust as ceramic glaze. Mind
you, I have no idea what happens to the chemical composition after
that and whether you can still call it jade.
It has been reported that purple jade from Turkey is being heated to
remove grey or brown overtones in it. This is being done in India
supposedly.
Lee Horowitz
Yes. And sometimes–like in The East Bay Firestorm of 1991 the jade
will absorb minerals or chemicals surrounding it. (That’s why it is
oftenburied with the deceased–enhancement in color). We pulled out
familyjade that was once medium light green and celery in color–it
became ash/creme to gray in color. And sometimes it was mottled.
Ciao from SFCA Jo-Ann Maggiora Donivan
“Jade Heat” is kinda catchy - can we make a movie? Nephrite jade is
a rock as well as a mineral. I posted a couple of years ago that the
assays on chemical composition of both the futurejade.com deposit and
Polar Jade (on the market) show that less than 10% of the rock is the
nephrite mineral and probably even less is the fibrous form of the
mineral which seems to act as reinforcing wire and gives the rock its
strength. Now if you have a jade deposit as we do, in a place where
there has been metamorphic action with pressure from local faults and
also apparently geothermal-epithermal action, the transformations
possible become huge. What will future First Nation miners find when
they run drill cores deeper into the deposit?
As you say, JJ, jade is absorbent. Over millions of years,
geologically the possibilities for asborbency variations are almost
unlimited. Perhaps Dr Rasmusen would be so kind as to give us his
geological opinion. The petrographic analysis says this is mantle
rock (which is only 3-4% of BC outcroppings) with its high Ca and Mg
content.
So why not “marinade” the jade and then subject it to heat? Think of
all the possible chemical transformations of the rock which are again
possible. I mentioned the yellowish-orange colours from kiln-firing.
I find them aesthetic but what would the final consumer say? Is
kiln-fired jade marketable even if it weakens or destroys the
nephrite reinforcing wire? Anyway I hope to have my new shop built
this summer - if I can do more tests I will post them here.
Also, given time for experimentation and a huge amount of jade I
have been running tests with the slabbing machine. The pattern is
highly variable as well as the colour and some of the patterns are
aesthetic. How marketable? We do not yet know. The colour range we
have goes from blackish to brownish to the typical jade green and a
very light, whitish green but colour intensity is not high so that is
why I say it is overall low grade. At the surface. What lies deeper?
There are some emerald green crystals but Gemological Institute of
America analysis says they are not nephrite. There is both organic
and inorganic C in the formation.
Your comments on burial traditions are interesting JJ. Do you know
the history of that tradition? Certainly royalty of China Mexico were
buried with their jade given that they tried to take their most
prized possessions with them. But the transformation of jade you
mention is another dimension. The royals would have seen the obvious
fact that mummification or not, the physical body does not hold up
well after a few centuries. Was jade burial transformation then a
symbol of the hoped for bodily transformation?
JADE TRANSFORMATION
Jade transformation then becomes the broader issue. The McHalsies
have informed me that their First Nation ancestors worked jade in
this region as well as shale-slate. Frankly I would be surprised if
they did not know of the stone-working prowess by their more distant
relatives in Mexico thousands of years ago and that would include
jade and gold work but it may not have been expedient to take up the
crafts here. Placer gold and jade may have been traded southward as
well as northward. The priceless transformer statue in the keeping of
Dr McHalsie at Sto:lo Administration looks to me like granite-family,
difficult as it is to see beneath the crusted exterior (page 35 of
Sto:lo Atlas by McHalse et al). However, the jade roadside cut/quarry
shown on our WWW is also the ONLY PASS to the 25 mile long Chilliwack
River Valley. Given the importance of that Valley and the Atlas
reporting on sacred sites (Atlas page 6), the “Jade Pass” must have
been especially important so I think they may soon proclaim this
quarry and the surrounding escarpment to be a sacred hands-off zone
placed exclusively under Sto:lo development. The page 7 map shows the
Chilliwack River in that valley to be a “transformer river”. The
listed rock/mountain transformers do not list the Jade Pass but I am
quite sure after years of prospecting the region that there is no
other jade deposit in that entire valley. Dr Keith Thor Carlson (also
an Atlas author) writes in “A History of the Chilliwack River Valley”
that archaeological findings in the Valley date to 4,200 years ago
(oage 23). It is also one of the “Rock Wall Fortification” as
described on page 52 of The Atlas and the Valley would have been a
fall-back position in times of war (page 50). That is why Canadian
Military had a base there for generations.
The Jade Pass then could itself be transformed if I understand
Sto:lo transformer cosmology correctly. It can be cut and carved like
the statue itself but how is of course up to the First Nations
people. The “jade incentive” is considerable. The escarpment is a
complex geological environment, not only to jade but metallic crystal
clusters and veinlets rich in gold, silver and platinum group metal.
The “slickenside effect” is more pronounced than any other rock wall
I have seen and the slickened coating is rich in precious metals
which suggests an epithermal cause and not the frictional effect
usually associated with the slickening. Therefore the prospect of a
bonanza precious metal deposit below is very real, as well as the
prospect of higher quality jade. Carving the jade rock face as a
giant transformer stone would help discover the validity of that and
this would explain the transformer cosmology to the public at the
same time.
M
refs -
A Sto:lo-Coast Salish Historical Atlas by McHalsie et al
In the Arms of the Mountains: A History of the Chilliwack River
Valley by the Chilliwack River Valley Historical Society, 2006 (Ch 2
by Dr Keith Thor Carlson and Ron Denman, titled “The Chilliwacks and
The River Valley”)
If you heat light green jadeite-jade, the material will turn white
under a jeweller torch. If the jade has been treated for example
B-jade (polymer impregnated jadeite), the jade will turn
brownish-black i. e. burnt polymer.
So be cautious when doing ring sizing with jade on it.
Regards
Tay Thye Sun
Yes, it has been in the news recently that purple jade that is heat
treated has hit the market.
Nick Royall
Yes, it has been in the news recently that purple jade that is heat treated has hit the market.
Do you know if it is labelled as (1) heat treated and (2) chemically
modified?
I am thinking that a skilled kilnsman could turn “junk jade” as I
have in almost unlimited supply into almost any colour after
“marinading” it in various broths but hey, what is it that
chemically?
This jade that’s being heat treated, is it nephrite or jadeite.
Do you know what color it starts as?
Derek Levin
no, it is heat treated. You cannot synthesise jadeite and if you
chemically alter it any portable xray analyser will spot it.
Nick Royall
I wonder what temperature it is heated to. Vince
Derek - I plan to do a lot more tests this summer on nephrite which
is low grade but our quarry has a huge amount and the colour range is
from brownish-orangey-yellow to light green, almost white, to medium
and dark green and black.
I want to standardize the tests by cutting some test pieces the same
size and varying the kiln temps.
Will post results to Orchid later.
Good Q on starting colour - so far it is a big factor on resulting
colour but all are in the yellowish-reddish-orange range (which
surprised me). Quite nice but is it still nephrite I wonder? How
would one know?
Kiln heating also weakens the micro-fractures in the rocks overall,
though some are like metal welds and stronger than the host rock it
seems.