Rainbow Calsilica - natural or manmade?

Jewelry Discussion
1

On another list, there is a request for a source for Rainbow
Calsilica. This is apparently a big seller for some people right
now. Some people say it is mined in Mexico and others
(mindat.org) say it is a manmade stone of calcite, plastic,
coloring and a parafin like material. Other than the actual citation
on Mindat, I can’t find anything to tell me any more about it.

Does anyone have a definitive answer to whether this is a natural
stone that is stabilized or something that is completely synthesized?
I’m personally inclined to believe the citation from Mindat. Rainbow
Calsilica looks “makey-uppy” to my eyes. I want to be able to tell
our customers EXACTLY what it is, because I know I’m going to be
asked. I’m already “educating” customers to the difference between
turquoise and “rare” White Buffalo Turquoise - aka howlite, so this
will make just one more “lesson” in my portfolio.

Thanks in advance to anyone who can help solve this puzzle.

Deb Weller
Weller’s Jewelry LLC
AZ Bead Depot
www.wellersjewelryandbeads.com

2

I believe it is similar to Fordite or Detroitite, but with some
ground-up minerals thrown in to fool folks into thinking its
natural.

According to Colored Stone,

  "Rainbow calsilica was a show-stopper at this year's shows, no
  doubt about it. With its bright striped layers of red-orange,
  blue, green, and yellow, it stands out in almost any crowd of
  It's hard to believe that a material like this could
  be produced in nature and, sadly, it isn't. 

  Rainbow calsilica has been sold as microcrystalline calcite in
  allophane from a mine in Chihuahua, Mexico. While the base
  material does indeed contain calcite, when scientists from the
  Swiss Gemmological Institute (SSEF) and Ghent University in
  Belgium examined a sample they found artists' pigments in the
  blue, yellow, and green layers, hematite in the red layers, and
  celestine in the black. "Our samples appear to have been made
  of pulverized carbonate rock that was mixed with pigments and
  stabilized with a polymer," concluded their report, which was
  published in the Winter 2002 issue of Gems & Gemology."

It is appalling that some people are still pimping this stuff as
"natural" on the web.

Lee

3

I just referred to this material in another post (about synthetic
emerald) as detroitite. Before a lot of automobile manufacturing
switched to Mexico, it was “mined” in Michigan as detroitite. That
is, if you call scraping thick layers of paint off the floor
"mining."

Most of this substance these days is slabbed to show the layers of
paint from the side, which yields a very colorful strata. I have an
actual (small) chunk of the Detroit material. It is in this form
that its real composition is easily determined.

Lab reports list the various components of it but, in the end, it is
paint. If you can find a piece that hasn’t been slabbed, cut it en
cabochon (which will show concentric rings of color) and mount it in
a bezel or prongs on a sheet of mokume gane as my friend, Tom
Stringfellow, did. It’s absolutely gorgeous. If it’s been slabbed,
though, you’ll only get parallel stripes.

James S. Duncan, G.G.
James in SoFL

4

Deb

Try this, http://www.colored-stone.com/stories/mar03/tucson2.cfm
about half way down the page.

  Rainbow Calsilica from Mexico 

  Rainbow calsilica was a show-stopper at this year's shows, no
  doubt about it. With its bright striped layers of red-orange,
  blue, green, and yellow, it stands out in almost any crowd of
  It's hard to believe that a material like this
  could be produced in nature and, sadly, it isn't. 

  Rainbow calsilica has been sold as microcrystalline calcite in
  allophane from a mine in Chihuahua, Mexico. While the base
  material does indeed contain calcite, when scientists from the
  Swiss Gemmological Institute (SSEF) and Ghent University in
  Belgium examined a sample they found artists' pigments in the
  blue, yellow, and green layers, hematite in the red layers,
  and celestine in the black. "Our samples appear to have been
  made of pulverized carbonate rock that was mixed with pigments
  and stabilized with a polymer," concluded their report, which
  was published in the Winter 2002 issue of Gems & Gemology.

Terry

5

What puzle?

Right on mindat.org:

  An artifical material created for carving/lapidary purposes.
  Contains a mixture of calcite, plastic and artifical colouring
  pigments (PB15, an art-supply pigment), and a parafin-like
  material. [ref: Winter 2002, Gems and Gemology, journal of
  Gemological Institute of America]

Wayne

6

I found this on the subject:

  Rainbow calsilica was a show-stopper at this year's shows, no
  doubt about it. With its bright striped layers of red-orange,
  blue, green, and yellow, it stands out in almost any crowd of
  It's hard to believe that a material like this could
  be produced in nature - and, sadly, it isn't. 

  Rainbow calsilica has been sold as microcrystalline calcite in
  allophane from a mine in Chihuahua, Mexico. While the base
  material does indeed contain calcite, when scientists from the
  Swiss Gemmological Institute (SSEF) and Ghent University in
  Belgium examined a sample they found artists' pigments in the
  blue, yellow, and green layers, hematite in the red layers, and
  celestine in the black. "Our samples appear to have been made
  of pulverized carbonate rock that was mixed with pigments and
  stabilized with a polymer," concluded their report, which was
  published in the Winter 2002 issue of Gems & Gemology.

I remember examples of calsilica selling on eBay last fall for $200 -
$300. Now you can get them for $ 10. I have a couple ($10 ones).
Interesting to look at, no matter how they’re made.

Brian Corll
Vassar Gems

7

I dont know if it is manmade, but did find this on an Ebay listing
from someone who sells it:

  There is controversy whether this stone is natural or man made.
  The original Geologist who did a scanning electron microprobe
  study of an untreated piece with rhyolite matrix attached,
  maintains that it is a natural stone and he could not detect
  anything that would suggest this is man made. GIA has published
  an article in Gems and Gemology stating that they tested a
  treated piece obtained in France, using Raman Laser
  Spectroscopy and it was found that the blue and yellow colors
  matched a man made pigment. They also said it had polymer and
  a paraffin-like substance. Since this article the source has
  sent treated and untreated samples as well a piece of the
  acrylic they use to stabilize it, to a Geologist/Chemist at a
  University Back East and he has faxed them his preliminary
  findings which I saw today and they clearly show that the blue
  and yellow does not match any man made pigments and no traces
  of paraffin were found. I will continue to post updates on my
  <snip> (see my "about me" page) as I know more and will
  obtain a copy of this report very soon. I cannot guarantee this
  is a natural stone since I am not an expert, but it is now
  looking like the GIA testing was incorrect at best and there is
  no solid evidence that it is man made and much evidence that it
  is natural. If it is man made, it's one of the best yet. The
  stone is beautiful and I like it whether if it is natural or
  not
8

Thanks Todd,

I already found this listing and wrote to the seller for more
specific - who was the geologist/chemist and which
“University Back East”. If there is a paper on this, I can track it
with that much

We bought some Rainbow Calsilica beads for the shop - whew, are they
pricey, but they are very pretty! They won’t get put up for sale
until I have a better handle on what they actually are.

Deb Weller
AZ Bead Depot
Apache Junction, AZ
www.azbeaddepot.com

9 
We bought some Rainbow Calsilica beads for the shop - whew, are
they pricey, but they are very pretty! They won't get put up for
sale until I have a better handle on what they actually are.

Deb, maybe this will give you a better handle on what they are. I
finally got off my but and took some photos of my chunk, or perhaps
a better word is “chip” of this material, created a personal web page
with my ISP and posted them there. You’ll see the photos at the
bottom of the page. Since it isn’t slabbed or fashioned into a bead,
you can see how it actually looks “in the rough.”

Folks, this stuff is automotive paint, plain and simple. It came
from Detroit in years past when it was jokingly called “detroitite,”
and now it comes from Mexico where auto manufacture is cheaper, and
called “rainbow calsilica.” It’ll probably come from India next.
Wonder what they’ll call it then?

James S. Duncan, G.G.
James in SoFL

10 
We bought some Rainbow Calsilica beads for the shop - whew, are
they pricey, but they are very pretty! They won't get put up for
sale until I have a better handle on what they actually are.

Deb, maybe this will give you a better handle on what they are. I
finally got off my but and took some photos of my chunk, or perhaps
a better word is “chip” of this material, created a personal web page
with my ISP and posted them there. You’ll see the photos at the
bottom of the page. Since it isn’t slabbed or fashioned into a bead,
you can see how it actually looks “in the rough.” Here is the URL:

Folks, this stuff is automotive paint, plain and simple. It came
from Detroit in years past when it was jokingly called “detroitite,”
and now it comes from Mexico where auto manufacture is cheaper, and
called “rainbow calsilica.” It’ll probably come from India next.
Wonder what they’ll call it then?

James S. Duncan, G.G.
James in SoFL

11 
Folks, this stuff is automotive paint, plain and simple. It came
from Detroit in years past when it was jokingly called
"detroitite," and now it comes from Mexico where auto manufacture
is cheaper, and called "rainbow calsilica." It'll probably come
from India next. Wonder what they'll call it then?

The difference, I think, between Detroitite and “Rainbow Calsilica”
IMO is that the latter has ground-up minerals intentionally added to
throw gemologists off the track. Detroitite, aka Fordite, was
comparable to Zincite (the Polish stuff) in that it was an
unintentional man-made stone, the chippings from the walls of auto
manufacturers’ paint booths. “Rainbow Calsilica” OTOH, is an
elaborate and deliberate fraud. I first saw the stuff in Quartzsite,
and got a whole sales pitch from the dealer complete with photos of
the supposed “vein” in the mine it was allegedly obtained from. It
didn’t look natural; it ISN’T natural. Many lapidaries were skeptical
about this material from the start, but at this point, with all of
the info available, I am inclined to say anyone still peddling it as
natural is either a buffoon or a scoundrel.

Lee

12

Doctor,

Thank you for the explanation. I think this batch of “rainbow
calsilica” is both batches we buy - first and last! Because I want to
be upfront with my customers about what we sell, I can hear the
conversation with a customer:

Customer: “Gee, those are very pretty beads, but they are so
expensive, what kind of stone is that?”

Me: “Well, it’s very unique. It comes from Mexico and believe it or
not, it’s just layers of auto paint.”

Customer: “And you’re asking $40/strand for AUTO PAINT?? That’s a
ripoff !!”

and the last we see is the customer walking off because he feels
insulted that we would try to sell clumps of auto paint as a stone at
premium prices. I have GORGEOUS hand carved malachite for a lower
price that is going begging. I can’t see “morphed paint chunks” (by
whatever name they are called this week) selling better than the REAL
stuff.

This conversation has led me on a search through “detroitite”,
“fordite”, “motownite” and “Detroit Agate” - an interesting journey.
Whatever it’s called, it is a pretty item.

I never did get a response from the e-Bay seller who claimed to have
an analysis from a “Geologist/Chemist” from some big “University Back
East” proving it’s a natural stone. I mentioned to the seller that I
have several contacts at “Universities Back East” - generally in the
geology departments, as luck would have it. And my hubby has a degree
in chemistry, so he would be able to translate such an analysis IF it
exists. Maybe I should quit holding my breath waiting for a reply?

All I can say for sure is - apparently in the beading world, this
stuff, no matter what it’s called, is selling like wildfire! So -
maybe it’s questionable heritage isn’t held against it, after all.

Deb
AZ Bead Depot
Apache Junction, AZ
www.azbeaddepot.com

13

If this is automotive paint (and I don’t doubt this for a minute),
then one wonders about the potential for toxicity when the "stones"
are worn against the skin. There may be cadmium pigments and other
nasties involved.

Brian Corll
Vassar Gems

14

As a test, I contacted six sellers of “rainbow calsilica” on eBay
and informed them of the probable identification of the calsilica as
automotive paint (hey - let’s call it “Duronite” !) or some other
pigmented material. Only one showed any real interest in finding out
what the stuff is. One said he didn’t care - as long as the idiot
public buys it, he’ll sell it to the idiot public. Four out of five
said: “Thanks for writing”. You know what that means. :wink:

Brian Corll
Vassar Gems

15

Assuming for a moment this stuff is automotive paint and sounds and
looks like it is (I worked as an auto painter years ago and seen this
layer effect), the potential for toxicity when the “stones” are worn
against the skin is a “maybe” in my opinion. As the paints don’t
leach with skin contact that I know of.

BUT, grinding, filing, sanding, burning… then things will get
nasty. If the paints are in fact from the 60’s and earlier (as I’ve
read) there can be any number of heavy metals, lead, cadmium and
dozens of other nastys (these are petroleum based paints remember)
that you really don’t want to breath or ingest inadvertently.

While it won’t likely kill you in a instant (well burning maybe it
could), long term exposure IS really bad.

16

I’ll add my 2 cents to the confusion. Recently I was speaking with
Archie of Archie’s Rock Shop in Mason, MI, USA and he indicated that
there had been a pottery factory in the area where the rainbow
calsilica is mined. It is his opinion that the factory workers simply
dumped the excess glazes out the door at the end of the day and that
the glazes percolated into the rock creating the layered effect.

“Fordite” is automobile paint that was dumped on the factory floor.
I’m no expert, but the layers in most “Fordite” cabs I’ve seen are
very opaque while the rainbow calsilica has a translucency that seems
different to me. So, I thought Archie’s explanation (pottery glazes)
seemed reasonable.

Debby Hoffmaster

17

If this is automotive paint (gee we live in a weird world.), then we
should start seeing some of the more recent madly popular metallic
copper colours soon, don’t you think?

Will be watching for it myself.

stephanie

18

Toxicity of Rainbow Calsilica

I have the same question about “rainbow calsilica” or “Duronite” as
I think we should call it. I wonder about the presence of pigments
such as the cadmiums which can be troublesome.

I just found a site on the web which references the composition of
topcoat automotive paints. Among the pigments used are the lead
chromates (yellow, oranges, etc.) and iron oxides. If you’re
cutting/cabbing any of the "newly found like Detroitite,
calsilica, or whatever, watch out for the inhalation of these
pigments, or transfer through the skin.

Brian Corll
Brian Corll, Inc. (BCI)
1002 East Simpson Street
Mechanicsburg, PA 17055

19 
All I can say for sure is - apparently in the beading world, this
stuff, no matter what it's called, is selling like wildfire! So -
maybe it's questionable heritage isn't held against it, after all.

First, Deb, you thanked me for my explanation and, you’re very
welcome. I would like to address the above, too.

The reason for that is because its questionable heritage is mostly
unknown. People everywhere are buying it under the assumption that
it is a natural stone because the people selling it are claiming just
that. It is a shame, because it really is pretty material that would
do well on its own, given the right marketing angle. But hanging a
name like rainbow calsilica on it and selling it as natural is just
criminal. The sad part is that if enough customers get angry about
being ripped off by this scam, our entire industry will suffer from
lack of consumer confidence.

Seriously, people pay lots of money for jewelry made with found
objects, beach glass and various “folk art” pieces. They’ll pay just
as much for paint beads, too. Remember pet rocks? There’s absolutely
no reason for anyone to intentionally mislead the public about gem
materials. It’s bad enough that some companies romanticize crappy
stones with weird misnomers, but “natural” rainbow “calsilica”
(“mined” in Mexico, no less), is going too far. Especially when they
know how many hobbyists there are on eBay and at the gem and jewelry
shows. Selling this stuff to them is like shooting fish in a barrel,
and it stinks on ice.

Please pardon my rant, I’m just an old hippie who still wants to buy
the world a Coke.

James S. Duncan, G.G.
James in SoFL

20 
I thought Archie's explanation (pottery glazes) seemed reasonable.

Sorry, but as someone who knows about pottery glazes, it is not
plausible. The glazes would have to be fired to have any color or
translucence, and fired glazes would be on pots, and would not be in
a form that could be dumped or seep into the ground… and on top of
that they don’t “spoil” so there would be no reason to dump them on
the ground.

Noel