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Andalucite? and general lab-creation question


#1

In the course of looking for interesting gems to set in my jewelry
pieces, I’ve run across Andalucite. I’m not that familiar with it,
but it is very pretty, with interesting color and clarity.

What concerns me is that the prices I’m seeing for it are all over
the map. One dealer is telling me it’s really rare, was only mined
for a very short time, and is hard to come by. Another dealer
considers it a “low-range” gemstone (whatever that means). A third
only deals in lab-created andalucite.

How can I get good and reliable info on this stone. I’d like to
work with it more, but want appropriate valuation guidance.

Also – what are your opinions of lab-created stones in general?
Are they as refractive and “beautiful” as their natural
counterparts? I’ve generally shied away from them in the past, but
I know the technology changes rapidly.

Thanks for any and all advice!
Karen Goeller
@Karen_Goeller


#2
      In the course of looking for interesting gems to set in my
jewelry pieces, I've run across Andalucite.  I'm not that familiar
with it, but it is very pretty, with interesting color and clarity. 

Hi Karen I get the feeling that some people (as I have on occasion
done) confuse Andalusite with Alexandrite. Vaguely similar names,
both of the orthorhombic crystal systems and both with their own
distinctive features.

My reference here is a little book called “Gemstones” by Cally Hall
(a handy book with great photos and pretty accurate in its info I’m
told) and I quote: “Andalusite varies in colour from a pale yellowish
brown to a dark bottle-green, dark brown, or the most popular
greenish red. It has very strong and distinctive pleochroism, so
that, when turned, the same stone may appear yellow, green and red.
Large crystals may be vertically striated prisms with a square
cross-section and pyramidal ends, but are rare. More usual are
opaque, rod-like aggregates of crystals or waterworn pebbles. It is
the pebbles that are usually cut as gemstones.” Occurences - “gem
gravels of Sri Lanka and Brazil. Other localities include Spain,
Canada, Russia, Australia and the USA.” Hardness is 7 1/2

There is no mention of rarity apart from that one crystal variety.

Alexandrite (which is a form of Chrysoberyl) on the other hand is
"very rare and valuable" and “changes from green in daylight to red,
mauve or brown under incandescent light, such as a light bulb.
Synthetic chrysoberyl, synthetic corundum and synthetic spinel have
all been produced to imitate alexandrite’s colour change.” In
regards to occurrence it states “although mainly worked out, the
best chrysoberyl, including alexandrite has been found in mica
shists in the Urals (Russia)”

There’s heaps more, but you may see from this the likelihood of
possible confusion amongst your informants.

As to lab-created (synthetic) gemstones versus natural. Beauty is in
the eye of the beholder. Actual brilliance must be the same in both
as they are the same mineral, ie your Alexandrite is a Beryllium
aluminium oxide and so is a synthetic Alexandrite, otherwise it is
not a synthetic but rather an imitation. It is the minute little
bits of other things that that make an alexandrite appear so
different from a crysoberyl cat’s eye (also Beryllium aluminium
oxide). Refractive index is the same for both. Personally, although
sparkly and pretty, the synthetic corundum imitating alexandrite is
not a patch on the real thing. I had the good fortune to see one
once. In natural light it was a deliceous deep blue green and under
incandescent light an intense pinky purple.

All that gasbagging and you were asking about Andalusite. Hope the
above was of some use though.

Renate from Adelaide, South Australia in the north of which state we
find another form of Andalusite, call Chiastolite which are cigar
like prisms which when cut in cross section have a cross-like pattern.


#3
    One dealer is telling me it's really rare, was only mined for a
very short time, and is hard to come by.  Another dealer considers
it a "low-range" gemstone (whatever that means).  A third only
deals in lab-created andalucite. 

Hey Karen, I have a hunch that there may be some confusion here
between andalucite and alexandrite…Adalucite is a relatively
inexpensive, strongly pleochroic gem: it will display 2 colors face
up at the same time (in many cases a brownish-green hue and a
brownish-red hue ). Alexandrite on the other hand is a much rarer and
very expensive stone. It also shows two colors, but under different
lighting conditions, not at the same time (ideally green or greenish
blue in fluoresenct/daylight, and red or purple in incandescent
light, depending on location mined). And to my knowledge there is no
lab created andalucite, but there is synthetic alexandrite. If the
stone you like is andalucite, great. If it’s alexandrite, well, I
hope you have a line of credit! (OK, I may be exaggerating a bit, but
not much!)

Cindy Crounse, G.G.


#4

Howdy Karen, I’m sure others here will have input based on better
trainig or more experience. The only andalusite I’ve faceted so far
had some ‘breadcrumbs’ and other inclusions, weighed 1.2cts. (not
bad from 2.2 rough weight huh?) GREAT red ‘c’ axis color and was a
modified ‘leaf’ or SF Pavilion=type cut. Great reds on the ends and
pale green in the middle. Sold it for $90 after carrying it to
severla shows a year for about 5 years. I love the material. I
suppose it is mineralogically most like tourmaline - as compared to
more commonly known gems. I’m not aware of a true synthetic though I
suppose anything is possible nowadays. Are you sure you’re not
confusing it with alexandrite? There is a lab grown chrysoberyl
available - nice though a little dark in larger sizes.

Carl
1 Lucky Texan