Group Discussion > Jade flaws

I have heard the terms "schistose" and "ex-foliation" used to describe jade rough. Could one of our mineralogists describe these flaws, and how they impact jade quality for carving?
May 2, 2007 | Unregistered CommenterAlan White
Alan,

I am not a mineralogist, but I am a jade carver and familiar with schistosity and exfoliation of nephrite. My experience with jadeite is limited. I have seen some minor lamination in jadeite which I perceived to be internal flaws. I suspect schistosity does not exist in jadeite.

If you have ever partaken of that delicious east European pastry baklava, you already have been exposed to schistosity and exfoliation. The twelve layers of crust of that dessert can be compared to schistosity. The outer layers that tend to flake away and fall into the lap while one is eating the pastry is exfoliation.

Nephrite jade is a metamorphosed product of the minerals actinolite or tremolite or a combination of the two of varying proportions. Each of those minerals are, in their own state, very sheathlike with parallel fibers. When the actinolite and/or tremolite are compacted under heat and pressure in the bowels of the earth, the parallel fibers of those minerals become contorted, intermeshed and compacted. The result is the very, very tough rock called nephrite.

Sometimes the parallel fibers of the original minerals have become compacted and intermeshed but not so much contorted, resulting in a product that is structured somewhat in parallel planes, hence schistose.

I have experienced schistosity in supposedly nephrite from Siberia such that when attempting to saw into thin slabs the material literally disintegrates into shards. Nephrite by definition is tough, and so that material does not qualify as jade. That is not to say that jade does not come from Siberia. On the contrary, Siberia has produced high quality nephrite. Other rocks, particularly the beach pebbles from Jade Cove on the California coast, characteristically exhibit schistosity and exfoliation yet the material often is a very tough rock qualifying it as jade which can be carved. Of course, the artisan must consider the schistosity when determining a subject for each piece.

When quality nephrite is sawn into very thin slabs of 1/16” thickness and held up to transmitted light the contorted and intermeshed fibrous nature, called felting, of nephrite can often be seen by the naked eye. If a “jade” cannot be sawn into 1/16” thin slabs, it cannot be carved and should not be called jade.

Schistosity in Jade Cove beach pebbles, if it exists, usually can be seen by the naked eye. A laminar structure will be readily observed on the edges of the stones. This may not necessarily preclude carving but it will visibly detract from the finished product. Not all Monterey Bay beach pebbles are schistose.

Nephrites these days are generally purchased by artisans directly or indirectly from mined sources. The ‘rough’ jade most often will be sawn on two or more surfaces. If two such surfaces meet at a corner, the prospective buyer can fairly well determine the carvability of the stone if it has some translucency. While observing the edge of the corner with transmitted light, if there can be seen a slushy or cracked ice appearance, the material likely is not suitable for carving. If there exists a nice clean edge with no, or very little, visible flaws, you likely will be able to produce a good carving. If the rough nephrite has only one or no sawn surfaces, you would be at risk purchasing such a piece without considerable prior experience.

From an experience basis, I would advise carving only nephrite that has at least some translucency.

My impression from your query is that you wish to carve jade or are in the early stages of doing so. I am responding with that in mind and am adding this final caution: be very careful making purchases from the internet auctions.

Hope this helps.

Dale Blankenship
May 2, 2007 | Unregistered CommenterDale Blankenship
Alan,

While I agree with Dale's comments, and especially thought his advise about checking the corner edge of two adjacent sawcuts apt, I have another take on your query.

If you look at the root words for each of these terms you have schis or schiz the same as with schizophrenia and ose as is found in fructose, sucrose etc. So what you can have here is a jade that may look very sweet but can turn on you in unexpected ways and may well drive you crazy.

The second term contains ex as referring to formerly attached to and foliate with the same root as foliage of course. This then refers to jade from the mythical Jade Tree. This jade was revered for its beauty but had to be worked within one year of being picked or falling from the tree and the lapidary had to be an honorable man or the jade would flake into worthless shards.

Any jade describable by either of these terms is a risk at best.

Be Well,

Tom Finneran

May 4, 2007 | Unregistered CommenterTom Finneran
So that's why some of my 'jade' fell into shards. I am either periodically dishonorable or I am working with overly ripe jade. Or maybe both.Perhaps over time I might be able to fix the honorable part,but I have not a clue where to find this mythical jade tree.

[I enjoyed your witty reply, Tom.]
May 4, 2007 | Unregistered CommenterDale Blankenship
if i may be so bold...i believe the mythical jade tree can be found on the slopes of the rock candy mountain...leeping far out of my own limited area with the two "true" jades i also enjoyed dale's reply in this thread...having recently being exposed to many new carvings, several slabs of raw material and a fabulous collection of estate cabs and carvings under the microscope, i have been noticing some anomalies with both nephrite and jadeite....some of these anomalies were lightly touched on by dale and i believe i will start another thread tomorrow to touch on these and perhaps stimulate some further exploration...be well, all...
May 5, 2007 | Unregistered Commenterdavid fredericks
Beautiful jade! Mistress of us all
In truth, says Dale, has many a flaw.
Tom and Dave agree,- indeed think it best
(To examine her closely, in a jocular way)
Ere diamonds do her sweet skin caress...


with apologies to all FoJ...
May 5, 2007 | Unregistered CommenterAlan White
I was under the impression that (generally) the very obviously schistose jades were of a higher actinolitic content. In most cases making the Jade chatoyant. High Tremolite content I think has (generally) shorter grains and more felted, and is less likely to have any cleavage surface.

I am looking right now at a pendant carved by Kevin Campbell that exemplifies an occurance where a tremolite jade body has later been penetrated by what I think to be a more actinolitic and siliceoues vein. The result is a chatoyant, less colourful, more translucent river in the existing body of jade. hmm I need to get a camera :)


oh yeah, my view is that if the natural chemical properties are in the correct proportions then it must be called jade. I guess there already is an anomaly called jade though, Na(Al,Fe3+)[Si2O6].

PS, I dig the caressing diamonds bit.




May 8, 2007 | Unregistered CommenterBrian