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Published: 2008-08-16 20:44:22 +0000 UTC; Views: 6412; Favourites: 184; Downloads: 126
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Description
(please click image for full view)Title: Black Opal
Image: Created by Aaron J. Greenblatt using an Epson Perfection 1200U scanner.
Editing: Edited in PhotoShop 7.0 for size, and to apply copyright and border.
Location: This black opal currently resides in my private collection in the lovely state of Michigan, USA.
Description: This is a natural black opal from Australia. I have hand sanded one side of this opal with fine sandpaper and hand polished it with cerium oxide. I did this to more clearly show the opal's internal beauty and color patterns. This opal is the size of a US quarter and has not been chemically treated or enhanced in any way aside from being polished. The color in this opal goes all the way through the stone and under just normal lighting conditions this opal radiates with splashes of color in all directions. Honestly, this image doesn't do this stone justice.
About Opal: Opal is a mineraloid gel which is deposited at relatively low temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, and basalt. The water content is usually between three and ten percent, but can be as high as 20%. Opal ranges from clear through white, gray, red, orange, yellow, green, shore, blue, magenta, rose, pink, slate, olive, brown, and black. Of these hues, the reds against black are the most rare and dear, whereas white and greens are the most common. The word opal comes from the Latin opalus, by Greek opallios, and is from the same root as Sanskrit upálá[s] for "stone". Opals are also Australia's national gemstone.
Information Source: [link] (wiki)
Legal: Copyright © Aaron J. Greenblatt. All rights reserved. Commercial use prohibited. This image and commentary may not be used for any reason without expressed written consent.
Please click here to view my photography work located in my Gallery.
Please click here for images of my glass work located in my other Gallery.
Please click here for images of my glass studio located in my other Scraps.
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Comments: 62
I knew this was a opal because i live in Australia
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This opal was fun to polish.
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Amazing array of different colors. Especially the specks of red and orange, and the neon green.
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Thank you. It's even lovelier in person.
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I've no doubt, cameras have an uncanny way of doing what they like with color and such.
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I actually didn't use a camera - I used a flatbed scanner.
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I guess it comes from all kinds of technology. My scanner enjoys doing that too. XD
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Even without doing it justice, that's still close to breathtaking.
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The black ones are my fav, stunning collection you have
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Thank you.
I'm actually more fond of the deep red and deep amber base colored opals myself.
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Though you say this photo does the stone no justice, this is one of the best photos I've seen, many people have trouble showing them even remotely accurately. Excellent work.
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Can I correct something for you here if possible..
Opal is formed (here at Lightning Ridge) under massive heat and large amounts of electricity. Volcanic fissures (or blows) that brought the silica to the surface, now opal clay, at that time then remained until almost recent times when almost 80feet of further strata layers have been deposited in some areas. Fairly large thrust faults (we call them steps and Z-walls also) and slides forced the ground to rip apart and caused the silica to settle and harden. Some of these faults displace the levels and sandstone roof etc. from one inch (usually where they start) to thirty feet apart in some cases. Everywhere there's gem quality opal found there is always a large fault close by. These create massive heat and static electricity when the shift, hence stabilizing and hardening the opal.
Len Cram (famous for his wonderful opal books) is a very good friend of ours and he's been creating opal for many years (think he studied chemistry). He put me onto these theories after not having enough electricity and heat available to harden or blacken his amazing home-made opal enough. We bought some of his only black opal in small amounts that he managed to fluke many years ago. It's far superior to Gilson as his opal has totally natural pattern structure and is in no way "plastic" like Gilson or Kyocera artificial opal.
I will photograph it and post it here soon along with some of our mineral collection. I'm looking for a decent macro lens for the XSi now lol.
Take care
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Very interesting information. However, many of my sources seem to state otherwise. In fact, the consensus among most geologists is that almost all Australian gem opal was formed by precipitation of silica from very dilute silica solutions or colloidal suspensions, derived from the deep weathering of feldspathic sedimentary rocks under the action of percolating groundwater.
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Yep that's partially true for the silica deposits. No argument there!
The formation of the silica into opal however is quite different. The silica sphere's (visible under powerful microscopes and are very interesting to see if you ever get the chance!) present in the opal only become settled enough to refract light once massive heat and electricity are present causing them to settle uniformly.
If these forces aren't correct and the spheres are in disarray this causes common potch opal formation. So given we have black common potch with settled silica colour bars on top or with it, does this mean several different stages took place? It's all the same silica but in very different stages of formation.
Now here's something that turns this volcanic ground water theory on it's head in a way.. My father found a patch of opal many years ago (the gems in my photos are from this patch) and in which he dug half a large gem quality nobby from the top of a white sandy blow(which were all one foot round and two feet apart)up near the sandstone roof and the other half of the exact same nobby at the bottom of the blow (around 5feet lower) so does that put the opal there before the active volcanic groundwater pipes were there to disturb it? Interesting no?
We come across many things here to dispute almost every idea that is put forward. Every one of the 7000+ mining claims here are sometimes very different in most respects. I guess there will always be a 'general consensus' but no one will ever really know for sure?
It's a shame you couldn't make it over to see it all for yourself? Like me, I'd bet you'd find it all very fascinating (and all a bit too contradictory for it's own good lol) It is eye opening to be underground and see just what happens and dig some opal first-hand.
It's so great to have someone that shares an interest in it! Most people I speak to just don't get mineralogy or geology, or, just aren't interested?
Take care and thanks for igniting my mineral-flame again
Very nice photo too! (I forgot to mention that)
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The silica sphere's ... present in the opal only become settled enough to refract light once massive heat and electricity are present causing them to settle uniformly.
Now that's an interesting idea - how exactly would the layers settle out and what would cause them to? I'm not so sure that precious opal layers can't be formed in nature over a large span of time and without much heat and electricity. For instance, other forms of silica (such as agates) are capable of forming intricate layers without much heat or electricity (that I know of).
Further, it would be kind of hard to explain the fossil opals if heat and electricity were needed - since technically both could potentially destroy most fossils before they could ever become opalized. So perhaps there are several types of scenarios in which precious opal could form. It wouldn't be unheard of, as other natural materials can form similar-looking natural structures under some varying natural conditions - which also could explain the slight to dramatic differences in color/shape/refraction/etc. between different types of opals.
does that put the opal there before the active volcanic groundwater pipes were there to disturb it? Interesting no?
Very interesting indeed. It should be noted though, that earthquakes (and here in Michigan, glaciers) are notorious for shifting things around and there could have been several different groundwater events in your area which also shifted material around - though perhaps didn't form opal.
Hence one reason why geology can be such a tricky science - there can be so many factors which had a hand in formation and deposition but which are hard to identify. Can you imagine what the first geologists thought when they encountered the warped and folded over layers of sediment found in most mountain ranges? It had to be a really big "WTF!?" moment for them.
I guess there will always be a 'general consensus' but no one will ever really know for sure?
Maybe not, that is until we actually see opal (with our own eyes) form in nature. And I don't know about you, but I don't exactly have a few millions years to sit around and watch it form.
Most people I speak to just don't get mineralogy or geology, or, just aren't interested?
I'm finding that there are a few people who are interested in Geology here on DA, but not many that have a lot of experience or knowledge about it. So yeah, in depth geologic conversations are hard to find here. Mostly because DA's user population is generally rather young.
And thanks for liking my photo.
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I was out fossicking around on the fields today (picked up a couple stones but nothing of quality) thinking about all these strange geologic things we've been chatting about and correlating them against what I've seen and found over the years of mining.
Dad and I talk a lot about the opal formation (amongst other things to do with minerals) and the "how the hell did fossils get opalised at the same time?" topic always pops up!
I was also thinking today why levels that are much harder than concrete still contain opal? The whole band of opal level is almost 100% silica but still allowed small nodule holes (possibly gas) for nobbies or seam to form. Many of the stones crack instantly upon removal as these hard levels put the opal under extreme pressure as you could imagine. I've dug opal out of very hard levels that actually spark and chip like flint when hit with a pick or jackhammer. That stuff is ridiculous and like shoveling roughly broken house bricks lol.
Ahh so many questions, so little time to work out all the right (or sane) answers! I'd love to have a few million years to sit around and watch minerals form as you said lol!
I'm busting to get a few photos of my mineral collection up here to show you and see what you think.
The agate banding is an amazing formation too! I love some agates, particularly the picture agates and black banded ones oddly enough? Your awesome glass pieces remind me so much of agate
Have you ever heard of, or seen a decent Polyhedroid Agate? (You seem to have very good knowledge of minerals so no doubt you have!) I have an exceptionally large one (about a foot long X 6in. X 5in.) and it's mostly black in colour. The thing looks just like a quartz crystal from the outside and is just a smooth. I've always been intrigued by the thing and have never seen another in the flesh?
My father also picked up a nice picture agate many years ago. Again it's black and white with an almost perfect Chinese temple picture inside. We don't have a large amount of specimens but we do have nice quality pieces
Take care A.J. and I'll see what I can do as far as photographing these pieces to show you (and anyone else on here I guess)
I'll start with the easily accessible pieces as we have everything boxed up ready to move house in the coming months. I'll do my best anyhow
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Your awesome glass pieces remind me so much of agate
There's actually now several types of glass rods which are called agate. Each rod is a combination of banded colors - one inside the other. When you melt the rod into a glass piece, the bands of color all swim about and the final piece comes out looking pretty darn close to how some agates look. It's a neat type of glass to work with.
Have you ever heard of, or seen a decent Polyhedroid Agate?
HA! Funny you should ask that! I just picked up three of them (each cut in half) at a mineral show last spring. They were sitting at the bottom of a crate full of round agates. Mine are white on the outside and get progressively darker towards their interiors with quartz crystal layers as well.
Unfortunately, the guy I bought them from couldn't remember what they were, let alone where he got them from. So while he gave me a great deal on them price-wise, I haven't a clue of their origin. One day I'll have to set one on my flatbed scanner and scan it in at a high resolution. It's amazing the sorts of details you can see in some agates.
Most of my specimens are also boxed up, mainly because I haven't unpacked them from moving here a few years ago. I've been meaning to get a nice display case but also haven't gotten around to that yet either. One day, though.
I also have yet to set up my lapidary lab. I have a rock slab saw, trim saw, and a number of grinding arbors with wheels as well as a flat lap. I'm planning on setting it up on the other side of my glass studio because I'll also be able to cold work my glass pieces on the machines.
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Hopefully I'll get a few "rough" specimen shots up today. I couldn't get hold of a macro so I winged it with the kit 18-55mm Canon (probably the worst lens out there lol)
Ha! What a score! 3 Polyhedroid pieces! That is so cool to hear!
I'll go and dig my better agates up if I can get to them and photograph our Stibnite specimen also.
I'm very jealous of your lapidary setup too
I'd love to see pics when you get it all set up!
Take care A.J.
Brace yourself for a few new photos
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Thank you.
It's nice to know that all of the "elbow grease" paid off.
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I agree. One day I will have to upload a small movie file that shows this piece as it's turned.
The colors are hypnotizing to watch.
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That's a real nice idea!
Hypnotize away...
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I'm actually surprised that there aren't more YouTube videos like that.
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excellent specimen and photo with a superb description
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