Agate

[Cave Keeper]

Is Agate a stone that evolved from fossil remains?

Is it possible for Agate to show magnetic properties?

What does someone mean when he claims Agate has the property of magnetic induction?

Is it possible for an Agate stone to comprise of 5% tektite?

What is the color of natural Agate?

 

[Michael_E]

Cave Keeper,
Agate is cryptocrystalline quartz. This means that it is composed of microscopic quartz crystals that all formed at the same time, or at least each layer within it formed at the same time. It's tought that the layers hardened from silica gels that became harder and more crystalline as the temperature and or water content lowered. I don't think that agate could be very magnetic since magnetism requires a high level of alignment among the iron or other magnetic metals that would be incorporated into the agate as impurities. Magnetic induction ? I don't know, sounds like a sales pitch. Normally inductive materials are metals and an agate would need a lot of impurities to get there, but who knows, could happen I suppose. 5% Tektite ? Only if the tektite were ground to microscopic bits and incorporated into the micro-crystalline structure of the agate. Natural agate without impurities is white since it is just a whole bunch of little quartz crystals stuck together. The impurities are what makes it attractive. Nickel salts in Chrysoprase, Iron oxides in carnelian, and who knows what in the fine blue agates. I think the most interesting are the fire agates which have layers of Iron oxide crystals which diffract and reflect light in an opalescent sort of display. Which are your favorites ?

 

[valeria101]

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On 10/13/2004 1:19:56 PM Michael_E wrote:


Which are your favorites ? ----------------

Sumatran chacedony and Elensburg blue below...

The images come from Premier Gem Design. No idea what these guys would not do wih agate. The site definitely does not tell the whole story. This is a very nice shop

 

[yowahking]

Agates are a whole gemology course by themselves. Some old guys can sit for hours showing samples of sites long played out. AZ fire agate is one of my favorites. I buy more than I sell which is the problem of many stone nuts. A few of the picture agates are so cheap for the once in a lifetime occurance of nature's painting. Mexico, Montana, Michigan, just a few pockets of interesting agates. Going to a rock show or hobby lapidary group is a cheap way to find really nice agate. I have customers often who bring in fantastic material bought very cheap that we recut for stunning designs. Just pulled an agate out of a belt buckle that sold at a garage sale for $5 that had an ugly silver plate buckle valued at $1, and an agate that was easily worth $200.

 

[Cave Keeper]

Your reply is worth reading 10 times, Mike. Thanks very much.

Agate is not exactly my favorite kind of rock. It just so happens the Tibetan dZi bead is made from Agate. And there seems to be all kinds of fantastic claims about dZi beads which leave me wondering whether those claims are true.

For example, there's a claim that Japanese scientists have found that the Tibetan dZi beads contain 14 different elements found only in meteorites.
And there's a claim that dZi beads can have a magnetic force of 13 Watts compared with 4 watts for quartz crystals (I didn't know magnetic force is measured in Watts). The dZi beads are etched Agate beads, but there's even a claim they dropped out of the sky. Another claim is that they are from the ground and were living, but fossilized immediately when caught by humans.

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On 10/13/2004 1:19:56 PM Michael_E wrote:

Cave Keeper,
Agate is cryptocrystalline quartz. This means that it is composed of microscopic quartz crystals that all formed at the same time, or at least each layer within it formed at the same time. It's tought that the layers hardened from silica gels that became harder and more crystalline as the temperature and or water content lowered. I don't think that agate could be very magnetic since magnetism requires a high level of alignment among the iron or other magnetic metals that would be incorporated into the agate as impurities. Magnetic induction ? I don't know, sounds like a sales pitch. Normally inductive materials are metals and an agate would need a lot of impurities to get there, but who knows, could happen I suppose. 5% Tektite ? Only if the tektite were ground to microscopic bits and incorporated into the micro-crystalline structure of the agate. Natural agate without impurities is white since it is just a whole bunch of little quartz crystals stuck together. The impurities are what makes it attractive. Nickel salts in Chrysoprase, Iron oxides in carnelian, and who knows what in the fine blue agates. I think the most interesting are the fire agates which have layers of Iron oxide crystals which diffract and reflect light in an opalescent sort of display. Which are your favorites ? ----------------

 

[Michael_E]

Cave Keeper,
This is funny, " And there's a claim that dZi beads can have a magnetic force of 13 Watts compared with 4 watts for quartz crystals (I didn't know magnetic force is measured in Watts). The dZi beads are etched Agate beads, but there's even a claim they dropped out of the sky. Another claim is that they are from the ground and were living, but fossilized immediately when caught by humans."
Although I'm not entirely skeptical of supernatural effects, (I just don't know on some claims), I am skeptical, when people fling around scientific jargon to support their claims. This one sounds like a really good sales pitch. Magnetism is measured in Gauss or if the field is more intense it's measured in Tesla units. Magnetism is a field, it is not power, which is what the units of watts represents. Quartz cyrstals are not magnetic under normal circumstances. In any case the beads that you mention may or may not have a beneficial effect. From my own experience I would have to say that the better they look, the better the effect...especially if you give them to someone else !

Scott,
You have got to post some pictures of your agates and other stuff ! I just love bright agates or better yet agates with intricate patterns. Almost as good as diamonds aren't they ?

 

[Cave Keeper]

Another seller on eBay claims that very old Tibetan dZi beads have a magnetic force of 12+/- volts compared with a force of 4+/- volts for quartz crystals.

The one that mentions magnetic induction claims genuine dZi beads can be tested by holding them close to each other, whereby because of magnetic induction they will either attract or repel each other. The few that he sent me failed the test, but maybe I misunderstood what he meant. I even tried testing for their magnetic property with a neodymium (NeFeB) magnet and found none.

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On 10/14/2004 4:13:18 PM Michael_E wrote:
Cave Keeper,
This is funny, ' And there's a claim that dZi beads can have a magnetic force of 13 Watts compared with 4 watts for quartz crystals (I didn't know magnetic force is measured in Watts). The dZi beads are etched Agate beads, but there's even a claim they dropped out of the sky. Another claim is that they are from the ground and were living, but fossilized immediately when caught by humans.'
Although I'm not entirely skeptical of supernatural effects, (I just don't know on some claims), I am skeptical, when people fling around scientific jargon to support their claims. This one sounds like a really good sales pitch. Magnetism is measured in Gauss or if the field is more intense it's measured in Tesla units. Magnetism is a field, it is not power, which is what the units of watts represents. Quartz cyrstals are not magnetic under normal circumstances.
:
----------------

 

[yowahking]

Michael,
I am happy to post some pictures of agate, I have promised a couple people pictures of spinel and a few other gems as well. Life just keeps getting in the way of picture taking.

 

[valeria101]

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On 10/14/2004 4:13:18 PM Michael_E wrote:



I just love bright agates or better yet agates with intricate patterns. Almost as good as diamonds aren't they ?

----------------

This must be some joke, right ? Everyone knows it is the other way around

!

 

[Richard M.]

While it's far from the best agate I've seen, here's one that's just right for Halloween -- a ghost (or is it a giant squid?) Both are scary.

Richard M.

 

[Cave Keeper]

I hope someone can post one or more images of fire agates, as I've no idea what they look like. My experience with agates are those Tibetan dZi beads, which are not exactly my idea of a beautiful gemstone. Only their supposed metaphysical properties will make me look at a dZi bead twice and consider paying $10 per year according to its age.

In fact, after looking at not quite a few gemstones, including the most disappointing Brazillian Paraiba Tourmaline, I think Precious Opal is the most beautiful gemstone and Ammolite second to Opal. I suppose that's why the Japanese are willing to pay $100,000 for the best Precious Opal. For that sum of money, one could get a few fantastic large whole museum-grade Ammonites at $1,000 per kilogram (personally, for the same amount of money, I'd settle for the equivalent amount of ammonites).

One terrific advantage Precious Opal has over Ammolite is the existence of large spherical stones; whereas Ammolite can only be more or less a surface stone.

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On 10/13/2004 1:19:56 PM Michael_E wrote:

:
I think the most interesting are the fire agates which have layers of Iron oxide crystals which diffract and reflect light in an opalescent sort of display.
:
----------------

 

[yowahking]

I will post some pictures of my fire agates, if you like opal and amololite, you should become a big fan of fire agate. There are only two sources for it, AZ and Mexico, although I see dealers selling it in Germany, HK, etc. Like many things, once you like it, you search the world for it. I feel sorry for drug users, at least I can still enjoy what I bought last week.

 

[Richard M.]

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On 10/18/2004 8:14:16 AM Cave Keeper wrote:

I hope someone can post one or more images of fire agates, as I've no idea what they look like.

----------------
----------------

Just seeing one fire agate image like the attachment won't tell you much. As Scott said above, agates (and the whole quartz family) are a gemology course in themselves. I'll post a few more images of finished stones below and look forward to seeing Scott's.

I polished this specimen while it was still attached to the host rock to illustrate how fire agate forms. The colorful thin layers of bright iron oxide (goethite) are deposited randomly through the brown botryoidal mass (botryoidal means 'like a bunch of grapes.') To finish it I'll eventually diamond-saw the polished section from the host rock, polish the bottom, then design a gold setting especially for this particular stone -- it certainly won't fit a standard mounting!

As with most gems, fire agate quality covers a huge range. There are many different colors, types, grades and "personalities," as with opal. In general, fire agate is a very much misunderstood and underappreciated gem. I spent years learning to cut it and, having cut most kinds of colored stones, can say that fire agate is by far the most difficult of them all! It requires carving skills along with normal lapidary techniques, and every finished stone is very hard won.

Fire agate is much more durable than opal (hardness 7 to 7.5 as opposed to 5.5 to 6) and it's much less brittle. Because of the way this particular agate occurs, jewelry usually must be made to fit the stone rather than forcing the stone into some preconceived shape. It's become a cliche lately in art jewelry circles, but this stone definitely tells you what it wants to be! If you ignore what it's telling you, the gem is ruined.

Anyhow I hope these images and others will provide more understanding of a truly fine gem. To date, notable fire agate deposits have been found only in the states of Arizona, New Mexico, California and portions of Mexico. It's also a "new" gem: prior to the late 1940s no one recognized its potential or knew how to cut it.

Richard M.

 

[Richard M.]

This fire agate from Mexico displays both purple and blue along with a spectrum of other colors. Purple and blue are rare colors in fire agate, blue especially. This large stone's colors are very bright.

Richard M.

 

[Richard M.]

This 13.67 carat stone (30 x 11 mm.) is a fine example of Arizona botryoidal fire agate. Extreme care must be taken in carving and polishing the "bubbly" surface because the color layers are extremely thin. Cutting through them can destroy an otherwise fine gem. Once a stone is properly cut it is very durable and jewelry-worthy. Releasing the beauty in this stone required many hours of painstaking work.

Richard M.

 

[fancyrock]

The above reminded me of an AMMONITE.

This is what my mom loves and i've gotten her 3 pendants.

 

[Cave Keeper]

I'm quite sure you're pulling our legs with that ammonite image, firerock.

I have yet to see a whole ammonite small enough to be a pendant which has the fantastic spectrum of colors which larger ones may have. What sizes were the ammonites bought as pendants for your mom, firerock, if I may ask?
So far, very small Alberta ammonites of less than 5 cm. (2 inches) diameter which I've seen seem very similar to their mundane Madagascar cousins in terms of gem quality.

But I agree with you that the fire agate examples kindly put up by Richard look very similar to ammolites.

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On 10/18/2004 4:58:04 PM firerock wrote:

The above reminded me of an AMMONITE.

This is what my mom loves and i've gotten her 3 pendants.

----------------

 

[fancyrock]

I'm sorry Cave Keeper, I didn't mean to get you excited like that! (wink**wink) I should have been more clear about what i got my mother. Her pendants were not a whole shell piece like the pic i posted. However, I did purchased an ammonite shell for her as a decorative item and it sits her living room. I don't recall the size of her pendants. I just bought one for her in May when I was in Alaska. I saw a beauty piece that I couldn't pass up. It has all the colors on one piece. I will try to post a picture tonight. (yes, i still have it b/c i haven't seen her yet. I am going home next month so i can personally deliver to her and see her happy reaction!!)

 

[Richard M.]

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On 10/18/2004 7:20:09 PM Cave Keeper wrote:

I'm quite sure you're pulling our legs with that ammonite image, firerock.

I don't think so Cave Keeper. The image (which should have been credited) is direct from Korite International's web site. It shows a complete ammonite fossil before being cut into smaller gems. While complete fossils from the Alberta site tend to be fairly large, these creatures occurred in many sizes, from huge to tiny.

I have ammonite fossils from France that have been replaced by pyrite and are just a little bigger than a dime (image). Since I don't know how to stitch images together in PhotoShop, see the next post for a different type.

The big advantage of fire agate over Ammolite and opal is its hardness. Fire agate is Mohs 7 to 7.5; opal 6 to 6.5 and Ammolite 4.5. Also, Ammolite and opal are cut into assembled doublets and triplets and Ammolite is treated with epoxy resin to stabilize it. Fire agate is entirely untreated and is sold only as solid 100% natural stones.

 

[Richard M.]

The "ammonite" in this image is pure iron pyrite which has totally replaced the once-living creature. Its remains were entirely decomposed before pyrite filled the opening in the limestone rock surrounding it, resulting in a "cast" or pseudomorph.

This specimen, from Germany, measures about 2 inches across. Ammonite fossils from other locations can be as big as truck tires.

The pieces of rock on either side of the ammonite cast are limestone that formed the original 'mold.' The entire piece was carefully chipped from the host rock then cracked open to reveal the fossil treasure inside. The collectors use a motorized wire brush to burnish these casts to a bright brass yellow. This one has oxidized a little in storage but could easily be brightened up again in a few moments.

The fossil ammonites from Alberta are the only ones I know of that have play of color in their shells. I posted the cause of the color play some months back but have forgotten the details. I believe it's a type of diffraction color similar but not identical to that in precious opal.

 

[fancyrock]

Here is my mother's pendant I bought in Alaska. This will be for her Christmas gift. It is from Korite Int. Alberta. That perfect ammonite shell is from their website. I didn't mean to say that's what i bought for my mom. I know I couldn't afford THAT!!

sorry about the picture, i don't know how to make it smaller.

 

[valeria101]

things get ? Until seeing this one below, I thought great fire agate comes only in fist-sized nodules...

 

[Richard M.]

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On 10/18/2004 10:57:35 PM valeria101 wrote:

How big do these things get ? Until seeing this one below, I thought great fire agate comes only in fist-sized nodules...



----------------

It's hard to tell how big even this one is considering the perspective of the shot, with the agate so close to the lens. It reminds me of the old fisherman's trick of holding a small fish at arm's-length right in front of the camera lens to make it appear like a whale.

It's clearly a much larger than average gem grade fire agate although it's not very well cut. Too much clear chalcedony has been left above the fire layers and the stone's full brightness isn't optimized. Still, an immense amount of effort clearly went into the polishing.

Over the years I've seen several carved specimens this size and larger at Tucson and elsewhere but they're not common -- at least to those of us who don't own fire agate mines! No one really knows for certain how fire agate was deposited though it seems to have resulted from some sort of hot-water (hydrothermal) deposition. It seems to come only from regions of the U.S.-Mexican Sonoran Desert where ancient extinct volcanic hot springs like those in today's Yellowstone Park were active over a long period. The silica and thin layers of colorful goethite appear to have dripped down slowly in water to form grown-together masses of miniature agate stalactites and stalagmites -- but that's my own theory based on reading and observation.

Bear in mind that these masses can be quite large. But only the ones with strong, bright fire layers qualify as gem quality, and they're few and far between. If the stone in your image is as large as it seems, I think it would be a fairly rare size.

 

[yowahking]

Nice pictures Richard, and bravo for learning to cut fire agate. So many cab them like cheap quartz in calibrated ovals and miss the wonder of this gem. I am partial to the combination of green and purple. Working on a jewelry art piece of a 300 ct specimin. Not the best cutting, but the shape lends itself to a cool design. One of the things that I will spend too much money on and have no where to sell it. My wife says there are a few things that will be auctioned off at my funeral, and some could cause the funeral.

 

[Richard M.]

Thanks Scott. I suspect our wives have something in common, LOL. Yes, I agree that the green-purples, when top gem, rival black opal but are lots more durable. I guess that's why they mostly go to market in Europe and Japan where they're more appreciated and we seldom see them offered here.

A 300 carat fire agate? Wow, this specimen only weighs 283 carats as-is and if I ever finish cutting it (it still needs lots of work) will yield 2 or 3 smaller -- but still large -- cabochons. This is one of the "Christmas Tree" red-greens from AZ. What sort of jewelry will you make with a 60 gram stone? Or will it be a sculpture?

Richard M.

 

[Cave Keeper]

Sorry, firerock, but your pix is shown only as an image icon (a small red box with an X inside), not the image itself. Maybe you need to repost.

Can anyone see the image?

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On 10/18/2004 10:52:37 PM firerock wrote:

Here is my mother's pendant I bought in Alaska. This will be for her Christmas gift. It is from Korite Int. Alberta. That perfect ammonite shell is from their website. I didn't mean to say that's what i bought for my mom. I know I couldn't afford THAT!!

sorry about the picture, i don't know how to make it smaller.

----------------

 

[fancyrock]

Sorry about the picture. Amateur at work here....
I was trying to edit the picture to be smaller, but instead i made it disappear. Can you see this one?

 

[elmo]

Richard and Scott, this is just too cool. Something I had no interest in at all, now you make me want to learn more. It's why I like to hang out here

, hearing about someone's hobby like this makes it pretty interesting. Thanks for the photos and insight.

 

[Cave Keeper]

Oh yes! I now know what you're talking about, firerock. Thanks for posting the pic of your mom's pendant finally.

Strange, when Richard posted the images of those large fire agate rocks, they did like similar to ammonites. But when you post the image of your ammolite pendant, I see ammolites and fire agate rocks are quite different. I mean, I recognize instantly that the ammolite was an ammolite.

Maybe someone could kindly post pics of fire agate cabs. Scott said he would post some fire agate images and we're still waiting for them, Scott. (Psst: Images of fire agate in cab, square, rectangle, marquis, round, oval, etc., form, if possible).

These stuff can be quite confusing. I could swear only today I saw 6 small pieces of precious opal ovals and hearts being sold as ammolites. I'm not into opal, but I've never seen ammolites so bright even in the shade so I'm quite sure they were opal. The shop was also selling ammolites, too, which looked 100% like ammolites would. But when the sales girl told me all the ammolites (including the 6 opal pieces) were from South Africa, my faith in the reliability of that shop's reputation diminished to Black Hole size.

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On 10/18/2004 7:31:03 PM firerock wrote:

I'm sorry Cave Keeper, I didn't mean to get you excited like that! (wink**wink) I should have been more clear about what i got my mother. Her pendants were not a whole shell piece like the pic i posted.
:
I saw a beauty piece that I couldn't pass up. It has all the colors on one piece. I will try to post a picture tonight.
----------------

 

[MerKaBa]

I had to hop in on this thread real quick b/c I simply love fire agates. The picture above is my prized Arizona fire agate posession. It is now set in a beautiful gold pendante accented by a few small diamonds.