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Rainbow Cal Silica


#1

Was browsing gems on eBay and came across slabs of this crazy stone.
The listing says it is new and there is controversy over whether it
is man made or not. It is layers of every color of the rainbow and
looks man made, but no one has been able to prove it. Can anyone out
there shed some light on this stuff?

Jill
http://www.jjewelry.com


#2

Jill, I bought a piece of it a couple of years ago when taking a
lapidary class. No one in the class knew where the stuff came from,
but a few months later the instructor spotted a short article on it
in Lapidary Journal. It is indeed man-made.

Mona


#3
    Was browsing gems on eBay and came across slabs of this crazy
stone. The listing says it is new and there is controversy over
whether it is man made or not.  It is layers of every color of the
rainbow and looks man made, but no one has been able to prove it. 
Can anyone out there shed some light on this stuff? 

Jill, before the NAFTA agreement, Rainbow Cal Silica was more often
called Detroitite. As in Detroit, Michigan. You know, where
automobiles are manufactured and painted. One seller on eBay cites
testing by GIA resulting in the identification of man-made pigments
and polymers. People around the world differ in their opinions of
GIA’s educational programs (I certainly don’t, I’m a GIA GG and an
alumnus), but few dispute their Gem Trade Laboratory’s abilities.

I have a smallish chunk (as opposed to the thin slabs you see on
eBay) of the early “Detroitite” which is most obviously comprised of
layer upon layer of…paint. Automotive paint. Don’t get me
wrong either, I’m not saying that just because it is paint doesn’t
mean it isn’t attractive or a jewelry possibility. One of the most
beautiful pieces I’ve ever seen was a cabochon of Rainbow Cal Silica
which was cut oriented parallel to the layers (with a sort of
rainbow wood grain look) and prong set on a flat piece of Mokume
Gane. Gorgeous! One of the funniest things I saw was a large quartz
crystal with several gemstones attached to it with wire. One was a
piece of this material that was shaped like a Zuni bear. It was made
by a Southwest Indian and was purported to have some kind of
metaphysical properties.

Anyone interested in viewing the chunk I have can contact me
off-list with this thread title in the subject line. If I get a
response, I’ll snap a photo and send it to you. If you’ve only seen
slices of this material, the photo of my chunk will illustrate for
you the true nature of this “gemstone.”

James in SoFl


#4

Rainbow Cal Silica is a type of epoxy paint. Poured out in coloful
layers, one on top of the other, then slabbed. Nice bright colors,
pretty, but not a naturally occuring stone, despite all the rants to
the contrary. I got clipped two years ago at Quartzite. Came
complete with a geologist’s report…totally bogus, but very
colorful. I continue to see it touted as the “real thing” by various
mall sellers. Ask any competent lapidary. I still think it is
pretty, but it is just a concoted item, like Detroitite or Mowtownite
(cut out sections from the walls of a well used paint booth that are
ground thru the various colorful layers then polished to resemble an
abstract Picasso-like painting.) Enjoy it…for what it is. Very
pretty and colorful!


#5

Last time this came up I think the majority opinion was that the
material was dried paint - of course my memory could be failing like
everything else!

Andy Parker, Agate House Lapidary
Ulverston, Cumbria, England
@Andy_Parker
www.agatehouse.co.uk
Tel: 01229 584023


#6

Perhaps you have run into the ‘‘true’’ rainbow obsidian. It’s from
the glass mountain area in Oregon. It has all colors and looks
manmade but is defiantly not! It’s a combination of transparent to
opaque material. One identifying marker is what look to be a
ruddybrown will transmit a brilliant red color when light is passed
thru.

Ringman


#7

Apropos “piece of this material that was shaped like a Zuni bear. It
was made by a Southwest Indian”

There is a particular “stone” found in genuine American Indian-made
turquoise jewelry (1920’s and 1930’s, I believe) which is a
translucent dark red. Experts were mystified as to the source of
this “stone.”

It turned out to be cut pieces of plastic. This particular plastic,
which looked so good next to turquoise, came from 6-volt automobile
batteries, which were encased in this material. The Indian
craftspeople found it in dumps, and cut it for jewelry.

Who is to say that it shouldn’t have been used? Same thing for
"Detroitite."

David Barzilay, Lord of the Rings

607 S Hill St Ste 850
Los Angeles, CA 90014-1718
213-488-9157


#8

Hi,

With some trepidation I’m going to add a bit to this topic.

The first year that Rainbow Calsilica appeared at Tucson I saw
unprocessed rough. It was very soft, a bit harder than chalk but not
much. The colors were there though not as bright as the processed
pieces.

The material is being processed by Colbaugh Processing, Inc who also
processes turquoise. Marty Colbaugh is importing this material from
Mexico. One of the large pieces that we bought wasn’t completely
impregnated with the stabilizing compound and it appeared to be the
same rough that I had come across.

There is controversy about the material. It was tested in Belgium
and was said to be made from “a pulverized carbonate rock mixed with
pigments and stabilized with a polymer”. A question that was raised
to counter that claim is that stabilized turquoise might also appear
to be pulverized rock mixed with a polymer when tested.

I called Colbaugh, Inc. (today) and they said that they had had the
material tested themselves and the results did not match that of the
Belgium folks. They strongly contest that the material is manmade.

The Colbaugh folks have a pretty good rep and I saw the rough for
myself so I’m going with the “its real but stabilized” theory.

If you get to Tucson, you might stop by their booth and check for
yourself.

Karen Dave