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Lapidary / Gemstone Community Forum
January 16, 2019, 05:29:53 pm
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Tiger Eye - What is it Composed Of?

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Author Topic: Tiger Eye - What is it Composed Of?  (Read 649 times)
James D. Farrow
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« on: February 18, 2016, 04:48:49 pm »

Hi!

I got some Tiger Eye rough (really rough) and on one side
there is a thin black layer of something and on the other side
there is a chocolate brown thicker layer (which is softer than the
rest).

Can someone tell me what these layers are made of?

I am assuming you grind/cut these layers off?

I tried the search function here but it gives me over 30 pages of
results of which most don't even contain "tiger eye".

Thanks,

James
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James D. Farrow
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Ranger_Dave
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« Reply #1 on: February 18, 2016, 05:25:16 pm »

Try this link: http://www.minerals.net/gemstone/tiger's_eye_gemstone.aspx
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James D. Farrow
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« Reply #2 on: February 18, 2016, 05:52:18 pm »

Thanks!

It mentions Hematite, which is probably the brown, but is says forms
stripes, streaks, or patterns within the Tiger's Eye.

On mine, the solid chocolate brown color layer (maybe 1/4" thick) is on the side and runs
the opposite way the tiger eye stripes run. Not mixed in with the tiger eye at all.
It's like the  tiger eye (stripes are up and down) is sandwiched between the softer brown layer
and the thin black layer on the other side.

James
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James D. Farrow
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asianfire
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« Reply #3 on: February 18, 2016, 10:54:10 pm »

A clean picture of you piece would allow people to give a straight forward answer. Everything else is pure guess.
As you saw at the recomended site, there are quite a few different types of Tiger eyes, and they go by different names. Hence you might have gotten 30+ pages in your search, yet not seen the type you have at hand.

Hematite usually shows up in a colour similar to a pencil mine (silver/grey).
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« Reply #4 on: February 18, 2016, 11:50:47 pm »

I have no idea what it is but it turns to mud when I sand it off....  dancer5

It is a common "matrix" stone that some tiger eye forms in but UGLY so get rid of it.
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James D. Farrow
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« Reply #5 on: February 19, 2016, 03:47:16 am »

Sorry, camera is still on the fritz. Have to get a new one.
That's another thread I have to start.

Yes, the brown layer is soft. Does grind off and makes like mud.

The tiger eye part though is hard like heck. Seems a lot harder
than the yellow jasper I have.

James
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James D. Farrow
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« Reply #6 on: February 19, 2016, 08:41:24 am »

Tigereye is typically found in an ironstone matrix which it typically composed of various iron oxides and loosely consolidated quartz grains.  This material is much softer than the tigereye and will typically form a brown mud when sanded or ground.  Occasionally there is a very thin black layer of manganese oxide between the brown layer and the tigereye.  In the older material, the miners typically cobbed off most of the brown matrix but that is not done as often today as they can still sell the material and weight is weight and weight is money.

Hope this helps

Bob Johannes
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bobby1
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« Reply #7 on: February 19, 2016, 08:54:57 am »

I always thought Tiger Eye was made of tigers with the black stripes being softer than the yellow ones, or am I wrong?
Bob
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« Reply #8 on: February 19, 2016, 01:50:25 pm »

I suppose, somewhere, there is a metamorphosed tiger.  dunno

Technically, tigereye is metamophosed crocidolite asbestos that has been nearly completed replaced by quartz.  The original crocidolite is naturally blue in color and the blue material has retained that color.  the yellow material has had staining of the quartz replacements fibers by the iron oxides.  Pietersite is similar but generally the asbestos fibers have not been as completely replaced by quartz.

I found a dealer this September who had a large quantity of pietersite and a number of the pieces were covered in loose fibers.  I asked if I could collect some of the fibers and had them analyzed and they are pure crocidolite asbestos.  Take care when handling pietersite as it may have a covering of no-repleace asbestos fibers which could adversely affect your health

Bob Johannes
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James D. Farrow
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« Reply #9 on: February 19, 2016, 03:08:44 pm »

Thanks everyone. Was just curious as to what it was.

Will grind it off.

James
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James D. Farrow
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James D. Farrow
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« Reply #10 on: March 06, 2016, 11:18:48 am »

On the piece of tiger eye I have, I ground down the brown (Hematite we assume) and
since it ground down nice and smooth I figured I would leave a thin layer of it and that
would be the bottom of the pendant.

Then I started grinding off the black layer on top. I figured one you get that off then the
tiger eye would show through. But it isn't. It still blackish (like the stone hasn't shaved
in a few days - LOL!).

Is it always like that? Do I have to have the orientation of the tiger eye stripes running
from left to right looking down on the pendant and not up and down looking at it from the
side? I thought maybe be then I would still have the blackish on the side.

Any info appreciated.

Thanks,

James (getting frustrated)

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James D. Farrow
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« Reply #11 on: March 06, 2016, 08:09:53 pm »

Tigereye must always be cut in slabs parallel to the fibers and at right angles vein of the piece.  If you are cutting across the ends of the fibers, all you will get is a black or brown stone with no pattern and no chatoyancy.  Not exactly sure from your description as to how you have the material oriented.

Good Luck

Bob Johannes
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James D. Farrow
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« Reply #12 on: March 07, 2016, 04:01:34 am »

The piece I have is about 1/2" thick. 2 1/4" long and 1 3/4" wide.
Sort of a heart shape. Laying it on the table the brown (hematite)
layer is on the bottom and the blackish layer is on the top.
You see the stripes running up and down on the sides all the
way around.

If I understand your post it looks like this piece will not work.
To have the stripes running left to right on top the piece would
end up only being 1/2" wide.

James
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James D. Farrow
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« Reply #13 on: March 07, 2016, 10:10:55 am »

It will work, just get creative. You can break it up and tumble it, or make a bunch of long, skinny, pieces. It would make some nice knife handles.
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« Reply #14 on: March 07, 2016, 10:18:03 am »

James

I happened to have a chunk of tigereye on my desk at work and took a couple of pictures to better help.

The first photo is a top view of a palm sized piece of blue yellow tigereye.  This shows some of the ironstone matrix that the tigereye seams form in.

The second photo is across the seam showing the fibers of the tigereye.  To show the chatoyancy of the tigereye the slabs must be cut across the seams.  My piece is about 2 1/2 by 3 inches and 1/2 inch thick so the widest cab I can cut from this piece is only a 1/2 inch wide.  If you were to grind down the ironstone on the top of the piece, you would be looking at the ends of the fibers and there would be no chatoyancy at all.

Bob Johannes
The Amethyst Rose



* Tigereye 1.JPG (2532.48 KB, 4288x3216 - viewed 6 times.)

* Tigereye 2.JPG (1912.28 KB, 4288x3216 - viewed 8 times.)
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mirkaba
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« Reply #15 on: March 07, 2016, 10:36:18 am »

I always thought Tiger Eye was made of tigers with the black stripes being softer than the yellow ones, or am I wrong?
Bob

:)
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Bob

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James D. Farrow
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« Reply #16 on: March 07, 2016, 11:30:45 am »

Looks like my piecce.

But even if you cabbed it that way (1/2" wide) as soon as you try
to round out the sides it will go blackish. Correct?

James
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James D. Farrow
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« Reply #17 on: March 07, 2016, 02:42:38 pm »

The long sides where the ends of the fibers are will be darker but the top of the stone and most of the way down the sides will be either the yellow or blue of the original tigereye.  The whole stone will not go black.

Bob Johannes
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James D. Farrow
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« Reply #18 on: March 07, 2016, 03:01:26 pm »

Thanks!

I guess I can play with it. Nothing to lose really.

James
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James D. Farrow
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« Reply #19 on: March 24, 2016, 11:58:58 am »

Tigereye is actually not a pseudomorph of quartz after asbestos.

Each fibre is in fact a quartz crystal.
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« Reply #20 on: March 24, 2016, 12:57:27 pm »

In mineralogy, a pseudomorph is a mineral or mineral compound that appears in an atypical form (crystal system), resulting from a substitution process in which the appearance and dimensions remain constant, but the original mineral is replaced by another. The name literally means "false form".

In the case of Tigereye, the original fibers were individual crystals of crocidolite which  have now been replaces with an individual crystal of quartz.  I thinks this meets the definition.  You could also call it a quartz replacement of cricodolite.

Bob Johannes
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« Reply #21 on: March 24, 2016, 02:52:31 pm »

Maybe not....

MinDat says this: A new interpretation of the origin of tiger's eye was recently given by Heaney and Fisher (2003): "Tiger's-eye is an attractive and popular gemstone that is ubiquitous in stores that cater to rock and mineral collectors. For more than a century, textbooks and museum displays have identified the material as an archetype of pseudomorphism, i.e., the replacement of one mineral by another with the retention of the earlier mineral's shape. Our study has revealed that the textures responsible for the shimmer of tiger's-eye do not represent pseudomorphic substitution of quartz after preexisting crocidolite asbestos. Rather, we argue that tiger's-eye classically exemplifies synchronous mineral growth through a crack-seal vein-filling process."

 dunno
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