Distinguish jet from black onyx

Hi, jet does not take as high a polish as does black onyx.
Also, there is no such thing as black onyx, it is white onyx
dyed pure black, and then marketed as black onyx. The easiest
way to tell the difference is to get some acetone-based nail
polish remover on a cotton ball, and rub it against it. If the
stone is a dyed stone, the black color will be rubbed off on the
cotton ball. To the best of my knowlege, they do not dye
genuine jet, therefore, anything that rubs off color, is a fake.

wednesday and thursday it snowed, and today it thinks it’s
spring (70*)!Yup, it’s April, and not December…

God bless,
Tom and Donna

Ok, Ok, I keep reading that there is no such thing as ‘black
onyx’. If that is true then what do I have that is as black as
it gets and is chalcedony? It is not dyed. I have seen "black
onyx, black agate, and also have some wood that is jet black.
All of these are as hard as any agate that I’ve seen. Yes, I
also have seen many things that are called black onyx that are
black something, but not onyx. Too soft. I have even seen
basinite passed of as black onyx. The only for sure dyed black
onyx that I have seen was more expensive than the natural black.
So, just what is “black onyx?”

thanks, fred

Fred, are you sure that what you have isn’t black (nephrite)
jade? And by what means do you have the knowledge that the
material you have isn’t dyed?

So-called black onyx is generally dyed chalcedony but, as you
observe, stones from basinite to fossil coal are lumped (pun
alert) together as “black onyx.”

Ken (gotta admit, I like rocks) Burchell

Hello Fred,

Black onyx is a jewellers misnomer, hardly deceitful or
misleading as genuine onyx is a calcite that is too soft for
jewellery and doesn’t come in black. “Jewellers black onyx” is as
you say anything that the jeweller can lay his hands on that is
black and shiny. I’ve repolished plastic, shell, wood,
lignite(coal), glass, ceramics, enamel and epoxy resin all
masquerading as black onyx.

On a really bad week I can get as many as a dozen blonyx jobs,
mostly inlay, and I always advise my customers that I use dyed
agate for maximum strength and integrity and advise them that
this is more expensive than ‘onyx’ which I will not guarantee.
Nobody has insisted I use onyx in the last 24 years so I haven’t
had to admit that I have no idea what black onyx is.

For certain applications I use other black stones, Sapphire,
Spinel and Dravite are all available in solid opaque black and
are all considerably harder than agate. Although black rough is
almost as worthless as black agate there is a lot more work in
preparing and finishing hence higher cost to the jeweller. Black
jade commands a higher price and is seldom passed off as the
cheaper blonyx, I use it for those trick jobs such as the ring
with the 4mm inlay channel with 3.5mm tube settings popping up
through …yikes how very artistic.

\ () || | /
\ /
\ /
ICQ# 15173706

Hello Fred,

Onyx is a variety of Chalcedony, and occur naturally. It has
alternating layers of straight black and white bands.

“Black Onyx” is a misnomer for black dyed Chalcedony. It is
obtained by immersing the relatively porous Chalcedony in a hot
sugar solution, and by carbonizing the sugar in warm sulphuric



   Ok, Ok, I keep reading that there is no such thing as
'black onyx'.  If that is true then what do I have that is as
black as it gets and is chalcedony? It is not dyed.  

Most of the commercially sold cut stones that are sold as black
onyx in the jewelry industry are a black dyed chalcedony. Most
of it started out as a rather nondescript greyish color. They
are often dyed AFTER cutting, and sometimes the dye doesn’t reach
all the way through.

However, the statement made in this thread that there is no such
thing as natural black onyx is not quite true. While fairly
rare, and sometimes a bit costly, naturally black appearing
chalcedony is indeed sometimes found. In most of the cases I’ve
seen, it’s not actually completely black, but is instead a very
dark brown, or even greenish. However, it appears black since
it’s so dark, plus the fact that it’s opaque. Placed next to the
common dyed commercial material, sometimes the natural doesn’t
appear as intensely black…

Also, some carnelian type material, which is commonly heat
treated to intensify the brown/red colors, turns such a dark,
opaque brown as to appear for all practical purposes, black.
While not actually dyed, this material can’t quite be called
natural black, either, since it’s been heat treated…

Telling the difference? Hah. Usually means you have to know
the miner… The dyed material is black due to plain old carbon
left in by the dying process. Not so easy to test for by ordinary
gemological tests… If you don’t already know, for sure, that a
piece is undyed, it’s usually safest to assume it’s dyed. Most
often, the assumption will be correct. For those who insist
it’s always dyed, I’d offer, as illustration, the many examples
of montana agate that appear clear to whiteish, only with intense
black markings and patterns inside. Those inclusions are, though
small areas in most stones, natural black chalcedony, right? And
I’ve got a few small cut stones of such material where the whole
stone is from a larger bit of such an inclusion. Occasionally,
the black areas of that material can be large enough to do that.
I offer that only as an example. Most of the usable black
chalcedony that I’ve seen is not of that type…

One general rule of thumb I’ve found useful in dealing with
gems… The words “never” and "always and “impossible” are
usually unwise choices in a description… Often they tend to be
at least slight overstatements…

Hope this helps.


Yes, I am pretty sure that what I have is not nephrite. It has
agate characteristics and not jade characteristics. Coccoidal
fracture and hard enough to “ring”. Although I have seen what
one dealer called black onyx and another dealer called black
nephrite. I am certain they were the same material from the same
location. of course the "jade was MUCH more expensive.

After reading some of the responses I do wonder about being dyed
though. How deep can the dye go I wonder. The piece that I
have is not too large, maybe about a pound. It fits into my hand
well. I don’t see any obvious clue to being dyed. The sure sign
of a good dye job I suppose.

I purchased it from a dealer that I highly trust. I would say
that if it is dyed, that he had no knowledge of it. I would also
add that he is not a dummy. But that does not mean that we can’t
all be fooled sometimes. I do think that it may be harder to
try and pass off a fake as something real than just stating what
it is. Where not talking expensive items here.

thanks, fred

Hello Peter, thank you for you informative response.

I failed to mention that the material I have is in the rough
form. Roughly about 4" to 5" diameter lump. Please excuse my
oversight. I personally would consider all cut “black onyx” to
be dyed. Just to be on the safe side, unless I cut it. And even
then it seems, doubt remains. I don’t know where this piece came
from, I didn’t ask. I will at my next opportunity.

A friend of mine that has a “black onyx” ring that is scratched,
wanted to get the scratches removed. When I tried to explain
that yes I could remove the scratches but didn’t really know what
the material really was, he became very defensive. I don’t think
that he believed me that the stone could be just about anything.
It still has the scratches.

I also have another piece of “black onyx” that every now and
then has a detectable brown line running through it. This piece
also is from someone I trust. I do find most people to be honest
and sincere. They could be sometimes mistaken though.

Thank all for responding to the this question that still
frustrates me. It is clear to me that I am not the only one
uncertain about this. Many are certain of an answer, but it
contradicts another certain answer. Just the way life is on
planet earth I suppose.

thanks, fred

This may be unethical, though i really don’t see why it would
be, but when there is a superficial scratch or scratches on a
dyed black onyx, I use a black indelible ink marker on the
scratch. It redies the scratch and also leaves behind a high
luster comparable to the polish on the onyx. This also works
for small scratches in malachite (green pen) and Lapis (blue).
It works well…

If i have ruffled any feathers,
Can we all agree to disagree?
And try to be kinder to one-another?

Take it to a gemologist and have a gem identification done.
Many have a lower price to the trade for an ID with no
valuation. There are ways to ID whether something is dyed and
they can tell you what your rock is. No reason to be

An observation: all of us in the various specialties in jewelry
get frustrated when the customer doesn’t understand or value our
skills. Yet sometimes we fail to value the skills of other
experts who could help us. (Or sometimes we value them, but
still don’t want to pay for them.)


Ok, Ok, I keep reading that there is no such thing as ‘black
onyx’. If that is true then what do I have that is as black as
it gets and is chalcedony? It is not dyed.

I’ve been following this thread with interest, since I still
have part of a (1995, I think) order from Goodnow’s. I finally
dug up the original description:

    Black Onyx, Africa - we've searched for a long time for a
good natural black onyx due to many customer requests, we
finally found it! Natural, hard solid black chalcedony cut by
professionals as black onyx. It takes a mirror polish. Great
for solid black inlay, cabs, spheres and doublets, etc. A few
pieces may have a few very thin white or brown lines, but most
pieces are solid black throughout. Only $10.00 per lb.; Sale
$5.00 lb. #20036 

I haven’t had it tested, but it certainly appears to be and
performs like black chalcedony, and the pieces I have are too
thick and uniform in color to be dyed.


Hi Al! I have some too! Undyed! Mine I got from Fire Mountain
Gem about 85’. Mine when held up to the light is really very
dark brown, with some zoning usually, The story I’ve got is
there really is not a lot of true black ever found or available.
But it does exist or at least what we have is real. Since we’re
the only guys speaking up; I wonder how much is really out
there. By the way, mine was very inexpensive a dollar or two per
cab. Lets hold onto it, someday we’ll be rich! Tim