Some less expensive labradorites are grey, ie, lacking the blue
"flash" seen in higher grade labradorite. Finding faceted
labradorites should be no problem.
Lorraine
Precious moonstone is micro layers of orthoclase interspersed with micro layers of albite.
The question is, what would make a nice faceted gray stone? I’d
agree that moonstone would be a fine choice. Whether it displays
adularescence or makes a nice Eggs Benedict is not the question. A
nice bluish-gray chalcedony might be another choice, though then
you’ll have a more opaque stone, most likely.
I can conclude by saying that what is called adularescence in faceted orthoclase ( we should not call it moonstone ) is not the adularescence, but simply a reflection of light from inclusions and other crystal irregularities.
Leonid, you’re wrong about this. Your description of adularescence
and it’s structural source is correct for the most part, but here’s
the thing: The reflection of light that adularescence describes is,
as you said, reflections from internal crystaline / structural
features of the material. The shape of the outer surface does not
limit this. It can, and does, act as a lens to focus the effect and
make it appear more the way we normally expect a moonstone to look.
However, facetting a moonstone does not eliminate the adularescense.
I have some very pretty blue flash moonstone which shows no
inclusions even under modest magnification. For all intents, a nice
eye clean stone, although faintly milky, as is most such moonstone.
The stone exhibits a bit of reflective brilliance, though not much
due to the low R.I. of moonstone. Enough to be nice though, as a
facetted stone. AND, it exhibits a nice blue flash OVER THE ENTIRE
STONE’s area. What is required for this is not specific facets in any
one place or another, but the correct orientation of the light source
to the stone. The individual facets do break up the flash some, so
it’s more visible on some facets than others, depending on viewing
angle. But at the right angle, most of the stone shows a nice overall
light blue flash. The range of effective viewing angles for these
stones is almost as wide as it would be for a cabochon. It’s clearly
adularescence, not some poor mimic in a related or heavily included
stone. And as you noted, this was not inexpensive material either.
The appearance of a facetted moonstone is different, to be sure, from
one cut as a cabochon, because the cab can act as a lens, while the
facets do not. A cab does indeed focus the flash, make it visible
through a wider viewing angle, and overall, works best in many
moonstones. But to say moonstone cannot be effectively facetted is
simply wrong. I know this simply because I’m right now looking at a
couple very pretty examples that demonstrate exactly this. As
facetted stones, they are somewhat more unusual than most moonstones,
and what they gain in interest and attraction from the facetting
quite makes up for any slight reduction in the strength of the blue
flash, which is still quite strong and distinctive.
Peter Rowe
Im not sure if this is correct ! I have a facetted spectrolite which shows the same optical effect, I assume from the same source? Providing the top facet is on the right plane the stone should still show the effect shouldnt it?
Moonstone is a special case. Spectrolite display is due to light
rays interfering with each other. Cabochon is still the best option,
but with proper table orientation it will have some display.
Leonid Surpin
Nice post. Very informative.
But…
No one mentioned “precious moonstone”. It’s hard to get, and
generally not grey anyway. I doubt any one on this list except you
would assume someone was talking about that when using the word
"moonstone". (Spectrolite is another thing that’s called moonstone
in some areas, but I wasn’t talking about that either…)
I specifically suggested to the original poster that grey moonstone
would work well as a faceted grey stone because grey moonstone is
easy to get faceted, and easy to get in general. It’s not helpful to
the original poster to pick apart what I suggested on inane
technical points that have no bearing on the topic that she asked
about.
Lindsay Legler
Dreaming Dragon Designs
The only difference between them is that for albite to form, potassium must be present; but orthoclase require sodium.
This is not quite true; albite is the sodium-rich feldspar, while
orthoclase is a potassium feldspar. (Just to help to keep the facts
straight.)
Richard Davies
The individual facets do break up the flash some, so it's more visible on some facets than others, depending on viewing angle. But at the right angle, most of the stone shows a nice overall light blue flash.
Here we go again. In gemological meaning “blue flash” is not
adularescence. It may look nice, taste is subjective, but it is not
adularescence, and it definitely not gray.
Leonid Surpin
The question is, what would make a nice faceted gray stone? I'd agree that moonstone would be a fine choice. Whether it displays adularescence or makes a nice Eggs Benedict is not the question.
I guess I failed to make a point that there is no such thing as a
grey moonstone. Moonstone is transparent and clear. Adularescence,
when present, makes it appear bluish-white (the most desirable) or
silvery-white. Everything else should not be called moonstone and
that is my point. The grey orthclase, which is marketed under the
name moonstone, when cut to display chatoyancy, should be called
wolf-eye, but not a moonstone.
Leonid Surpin
Here we go again. In gemological meaning "blue flash" is not adularescence. It may look nice, taste is subjective, but it is not adularescence, and it definitely not gray.
Lighten up. I did indeed mean, and it very much IS, adularescence.
And it is often called “blue flash moonstone” by dealers to
distinguish those often priceiest of moonstones where the color of
the adularescent reflection is light blue, rather than white. I’d
point out that the stone itself doesn’t care which word I happen to
use, and “blue flash” is a lot quicker and easier to type and
doesn’t need me to wonder if I’ve misspelled it… If I happen to use
the less precise common term, that does not mean the stone is not
still moonstone. I’ve even seen that label used in formal gemological
articles from GIA or elsewhere. Sure, it’s informal imprecise
terminology, but everyone ELSE on the planet, Leonid, seems to know
what it refers to. If asked what the proper name for the effect is,
I’ll give the correct finger twisting answer. In the middle of a
conversation about what’s understood already to be moonstone, well,
maybe not. Do I have to be consistantly more formal with you? Geez.
Oh, you’re right, though on part of that. The moonstones where the
reflected light is light blue, at least the ones I’ve seen, are
always colorless and at least mostly transparent, rather than
transluscent or another body color.
Some of the others, with white adularescent reflections, can often
be found in other low intensity body colors, from grey, to tan,
peachy tones, etc. Much of it is from India. And yes, this stuff IS
indeed Moonstone too. Some of it is quite pretty when cut well. And
being transluscent, rather than transparent, you’d be right in
suggesting that facetting isn’t a good way to cut such material…
Peter
Ok, Anyone in Need of Gray faceted or cab moonstones please contact
me offline.
Ahmed Shareek
I guess I failed to make a point that there is no such thing as a grey moonstone. Moonstone is transparent and clear.
Leonid, perhaps you’ve been too spoiled, using only the finest of the
moonstones. True, the best stuff is indeed usually clear/colorless.
But there’s also a lot of moonstone, and YES, it’s still moonstone,
though of lower quality, that is more transluscent, and has some body
color. Gray is common, as are peach / tan/ light brown tones. Much of
this material seems to come from India. Gemologically, it remains
moonstone. Not common with the prized blue adularescence, though.
Usually just white flash…
Peter
This is not quite true; albite is the sodium-rich feldspar, while orthoclase is a potassium feldspar. (Just to help to keep the facts straight.)
You right of course. I was trying to express dependancy of formation
of one on presence of the other and sentence came out really twisted.
Thanks for pointing it out.
Leonid Surpin
It's not helpful to the original poster to pick apart what I suggested on inane technical points that have no bearing on the topic that she asked about.
I could not agree more, Stick to the basic points and less on the
theory, which only adds confusion to a very simple original question.
Ivan.
Leonid, perhaps you've been too spoiled, using only the finest of the moonstones. True, the best stuff is indeed usually clear/colorless. But there's also a lot of moonstone, and YES, it's still moonstone, though of lower quality, that is more transluscent, and has some body color. Gray is common, as are peach / tan/ light brown tones. Much of this material seems to come from India. Gemologically, it remains moonstone
I am not sure if I agree with the term “spoiled”, but I hate
simplifications and bundling everything under one convenient term.
We do not do it to corundum. We do not call everything Pigeon Blood
Ruby.
We have carefully created several names for each and every variety,
but we have no problems calling moonstone each and every member of
feldspar group. This does not make sense to me.
Leonid Surpin
I am not sure if I agree with the term "spoiled", but I hate simplifications and bundling everything under one convenient term.
OK, I’m sorry. You’re not spoiled. But I was implying that perhaps
you were used to only the best stones, which would not surprise me,
considering the fine quality of your work. If that were the case,
then perhaps you’d simply not worked with, and be sufficiently
familier with, the lower quality moonstones…
However, in no way was I ever bundling everything into one term. The
only term I played a bit loose with was calling blue adularescence
“blue flash”. That bundles nothing, as it refers to a quite specific
and desireable type of moonstone.
Note that there ARE different types of moonstone, and they are all
moonstone, not other varieties of feldspars. I fully agree with you
that the others should be called by their own names, and not bundled
into the word “moonstone” unless they gemologically are indeed that
material. However, the term moonstone does not limit the body color,
or the transparency, or the color of the adudularescent reflection.
It specifies the composition and structure of the material, which
will then produce that adularescence. There are indeed clear
moonstones, and somewhat lower quality, cloudier, and with body
color, moonstones. In the same way that as you note, we don’t call
all rubies pigeon blood unless they fit that description. But other,
lesser quality red corundum is still ruby. This is the same. Body
color variations, or variations in transparency, do not negate the
identification of the stone as moonstone.
We do not do it to corundum. We do not call everything Pigeon Blood Ruby.
I fully agree. But if it IS corundum, and it falls within the red
color range, then we DO call it ruby. Just as Ruby comes in various
qualities, price ranges, and variations in color, so does moonstone,
as do most other gems. Moonstone, as has already been carefully
described in this thread, refers to a specific chemical makeup within
the feldspar family, as well as the layered structure that gives rise
to the adularescent effect. The term does NOT specifically define an
exact look, color, or cut. To do that we’d need more descriptors
added to the term “Moonstone”. Thus one might see “blue flash
Moonstone”, which more closely narrows down just what the stone looks
like, even if the term “blue flash” is not a properly defined
gemological term, just as the term Pigeon Blood isn’t exactly part of
any of the developed color description systems for ruby. It IS,
however, a traditionally used term, and though people sometimes have
variances in what they’d call “Pigeon Blood”, it’s pretty well
understood roughly what that means. The same, from what I’ve seen,
for the phrase “blue flash” as applied to those colorless,
transparent, moonstones with a blueish adularescent effect.
We have carefully created several names for each and every variety, but we have no problems calling moonstone each and every member of feldspar group. This does not make sense to me.
We do NOT call every member of the feldspar group moonstone. Not at
all. Labradorite, is labradorite, not moonstone. Sunstone is
Sunstone, not moonstone. And so it goes. Distinct varieties worthy
of their own name generally have one. Non-descript versions may
simply be referred to as whatever mineralogical version of feldspar
they happen to be, but they are still not, as you say, Moonstone
unless they fit that definition. Moonstone, as you and others have
already nicely defined for us, is a specific structure and
composition within the feldspar group. There IS some variation within
that definition that still fits the proper use of the term moonstone.
Nothing I’ve said in this thread, or that others have said so far as
I recall, is at odds with your desire to keep the term well defined.
Peter
All that have replied to my post. I really appreciated the time
everyone took to reply to my post.
The question remains, which has been misunderstood, what specific
Treatment can be used to create a grey faceted gemstone?
Gemstones that are treated are dyed, irradiated, heat treated,
oiled, etc. Topaz & Diamonds are irradiated, Citrine is heated
Amethyst, Emeralds are oiled, Turquoise is dyed - are some examples
of Treatments given to enhance or change a color of a stone.
In 1984 a book was written by Kurt Nassau-Gemstone Enhancement. It
is out of print. It is suppose to have “cook book” section on
specific treatments.
Sincerely,
Terri Sidell
The question remains, which has been misunderstood, what specific Treatment can be used to create a grey faceted gemstone?"
Do you want opaque, translucent, or transparent. I do not think there
is a transparent gem that appears gray, so there might not be a
material that can be treated to be gray.
The gems I know that are gray are cabbed silliminite and cabbed
moonstone.
You might be able to dye howlite and facet that material and you
will have your gray faceted gemstone, opaque, but gray. There might
be some opaque material you could heat and produce a gray gem
material. Why gray?
Richard Hart G.G.
Jewelers Gallery
Denver
The question remains, which has been misunderstood, what specific Treatment can be used to create a grey faceted gemstone?
Grey color is not what most of gemstone buyers are looking for and
because there is very weak, even non-existent demand for grey
stones, nobody is going to invest valuable time to invent one.
If you looking for an attractive grey stone, consider grey diamonds.
There are plenty of them around. Another alternative is use
gemstones with grey pleochroism. In normal practice, gems are cut to
minimize appearance of grey, but in your case cutter can emphasize
grey direction. Blue iolite is one of such gemstones as many others.
Schorl is usually black, but some stones faceted with table parallel
to c-axis could show grey. And many other possibilities exist, so you
can see there is no need for a treatment to create grey
Leonid Surpin
Peter,
Makes me wonder if using the curved facet units sold by at least
Zane Hoffman, would make a difference.
Hugs,
Terrie
In 1984 a book was written by Kurt Nassau-Gemstone Enhancement. It is out of print. It is suppose to have "cook book" section on specific treatments.
Well, sort of. It describes the treatments in decent detail to allow
the reader to understand the nature of the process, but not with
exact specifics to teach you to actually do it. It’s a descriptive
gemological text, not an instruction manual. None of the treatments
described are to give a grey transparent gem as the intended result.
Not surprising, since there’s virtually no real demand for that end
result (other than you, of course.) The grey’s and blacks generally
found, including in Nassau, are dyed chalcedonies or opals and the
like… At least, that’s all I saw looking through my old copy…
Peter