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Idcocrase/Transvaal Jade


#1

Ron, Yes, I’ve cut a fair amount of massive California idocrase but
haven’t seen any rough in a long time. Aren’t idocrase and
vesuvianite the same thing, or am I missing something? I know there
are massive and crystalline varieties (facet grade). Is that the
distinction?

The idocrase I worked with was called “Happy Camp Jade” but it
wasn’t jade even though I know there’s supposed to be a jade claim at
Happy Camp. I’ve also worked with material from Pulga.

None I’ve seen has any garnet present, which is what I believe
distinguishes the so-called Transvaal Jade. The article about it
gave the impression that it made quite a splash in the 1940s and the
Idar-Oberstein dealer presumably cornered the market by buying up
most of the rough but then failed to cut and promote it. I’ve read
about it for years but had never actually seen any until the
so-called “Watermelon Garnet” arrived. Maybe that’s why you didn’t
see any in your African travels. But there must be more than one
source because even though the Connecticut dealer is said to have
bought up the German supply, stones, some with very high prices, are
coming out of Bangkok. Thaigem has pictures on its site.

Rick Martin


#2

Dear Richard, John Sinkankas devoted a considerable amount of
attention to idocrase in his “Gemstones of North America” Indeed, he
included those references in the chapter called “Important
Gemstones” Other stones in this chapter included jade and
tourmaline. It is evident that John had a high opionion of idocrase.
It is also apparent that he preferred to call the California
idocrase Californite. And, one of the reasons that he isolated
California occurences of idocrase is that the material was nearly
always associated with white grossularite garnet. The Happy Camp
variety is a good example of that association in that the areas of
idocrase and garnet are quite separate and distinct.

One of the amusing aspects of idocrase is that so many names have
been applied to it…idocrase, vesuvianite, californite, California
jade, Happy Camp jade, etc. etc. And then there is the further
complication of there having been jade recovered in the vicinity of
the Happy Camp mine. And then there is the really unique incidence
of there having been jade from that locality which contained flecks
of gold !

As for faceting idocrase, the only California idocrase which has
been faceted is that which occurs at Pulga in Plumas County; this
material does have an occaisional degree of high translucency, but
it cannot be characterized as a suitable faceting material because
of its lack of transparency. However, the degree of translucency is
sufficient to give it a kind of glow which is distinctive.

The Pulga material has been mined recently and a certain amount of
the material has made it to market, but market acceptance has been
hesitant, to say the least. I have made a dozen cabs from it and
would liken it to some of the lighter hues of Siberian
Jade…except that it has the distinctive glow. The color is
remarkably close to that of the San Carlos peridot in Arizona.

The only facet grade idocrase that I know of is that which occurred
in Quebec, Canada. It ocurred in euhedral crystals up to four inches
in length, but very little of it was suitable for cutting. It should
be noted that the California type of idocrase also occurs in Oregon
and I have seen references to occurences in Washington state.
Indeed, there are known occurences throughout the world, but the
type that is intermingled with grossular and which has the physical
characteristics of jade is most closely associated with the
California occurences. Ron at Mills Gem, Los Osos, CA.