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Post by dreamrocks on Jun 23, 2024 18:13:49 GMT -5
Oops sorry
Any agate is fun to cut and polish, I would post some pictures of the stuff I have finished but unable to post pictures nor can I add any posts also have a sweet geode I recently cut. So I put this up to see if I can add to profile nothing else will.
Really pretty, even though you can’t show it fully, I can imagine it. Nice cab cut too and pretty good size. Did you have to cut it out of matrix? And, are these opals ones that you have to worry about drying out? I know some they say to keep in water or to wear often. Might be a whole nother topic… I haven’t gotten into opals yet because it seems to require an expertise.
With Ethiopian opal from Welo the problem with water is just the opposite. It's a type of opal called hydrophane, meaning basically it's "thirsty" opal and the play of color disappears when it absorbs water. It usually comes back after a few days when it dries, but sometimes the opal cracks and is ruined. Sometimes it just doesn't come back.
But not all Ethiopian opal is hydrophane, including some from Welo. There are several other opal producing areas there and some produce stable opal. One of the worst for cracking, however, is the so-called "chocolate" brown opal that comes from thundereggs. It has its own beauty but like most "volcanic" opal from worldwide sources, it's very "cracky." Australian opal is generally much more stable and the main commercial types are sedimentary rather than volcanic in origin.
There's also a type of opal I've encountered from Mexico I call "reverse hydrophane." A relative gave me a bottle of reddish-brownish Mexican opal she'd brought back from a trip. It was peddled on the street by kids to tourists. None of it showed play of color. I decided to make a cab from one of the prettier red pieces and as I was cutting with water it suddenly burst in to bright greens, reds, oranges etc. I was excited but the colors, in opposite fashion from Welo, disappeared when it dried.
Opal is fascinating stuff. There's another type called "contra-luz' (against the light) that shows play of color only when viewed with light transmitted through the body of the stone, not reflected. I've run into it only in opal from Mexico and from a well known locality in Oregon whose name I can't remember at the moment. The opals from Spencer, Idaho, rarely display true cat's-eyes and stars when cut as triplets. None of that type are known from any other source.
Getting back to your water question, all precious opals (the ones that show play of color) contain varying amounts of water. When it dries out, say in low-humidity environments, they can craze and break apart. Fine opals stored in bank vaults are very susceptible to crazing because the vaults are kept at very low humidity to preserve paper documents. The rough opals one sees at gem shows are usually kept in water for display purposes only, to show off their colors. The water also magnifies their size and hides cracks and other blemishes. Rule of thumb: always buy your rough opal dry.
Why is it so hard to capture the color and brilliance once you photograph/film it? Frustrating as all hell. Color is way nicer in person.
Anywho.... I've been cutting opals. Once I can figure out this whole photographing thing i'll post a whole thread. Just wanted to share a lil ripper I cut this morning.
Opals are a bitch to photograph. See if you can get a better picture by putting it in a black container with water and taking the picture through the water. Direct lighting on opals just washes them out. Indirect sunlight is best, but indirect artificial lighting will work too. Just maybe not as well. Just don't put those Ethiopians in water. Hydrophane little buggers.
Yours looks like a nice one! Nice cutting, too.
Robin
"Of all tyrannies, a tyranny sincerely exercised for the good of its victims may be the most oppressive. It would be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated; but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience."
Call me biased (you can; it's my middle name) but Australia has the nicest opals. Really loved seeing this. Nice work, despite the photo challenge.
Agreed! Australian opals are the best.
Robin
"Of all tyrannies, a tyranny sincerely exercised for the good of its victims may be the most oppressive. It would be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated; but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience."
Really pretty, even though you can’t show it fully, I can imagine it. Nice cab cut too and pretty good size. Did you have to cut it out of matrix? And, are these opals ones that you have to worry about drying out? I know some they say to keep in water or to wear often. Might be a whole nother topic… I haven’t gotten into opals yet because it seems to require an expertise.
With Ethiopian opal from Welo the problem with water is just the opposite. It's a type of opal called hydrophane, meaning basically it's "thirsty" opal and the play of color disappears when it absorbs water. It usually comes back after a few days when it dries, but sometimes the opal cracks and is ruined. Sometimes it just doesn't come back.
But not all Ethiopian opal is hydrophane, including some from Welo. There are several other opal producing areas there and some produce stable opal. One of the worst for cracking, however, is the so-called "chocolate" brown opal that comes from thundereggs. It has its own beauty but like most "volcanic" opal from worldwide sources, it's very "cracky." Australian opal is generally much more stable and the main commercial types are sedimentary rather than volcanic in origin.
There's also a type of opal I've encountered from Mexico I call "reverse hydrophane." A relative gave me a bottle of reddish-brownish Mexican opal she'd brought back from a trip. It was peddled on the street by kids to tourists. None of it showed play of color. I decided to make a cab from one of the prettier red pieces and as I was cutting with water it suddenly burst in to bright greens, reds, oranges etc. I was excited but the colors, in opposite fashion from Welo, disappeared when it dried.
Opal is fascinating stuff. There's another type called "contra-luz' (against the light) that shows play of color only when viewed with light transmitted through the body of the stone, not reflected. I've run into it only in opal from Mexico and from a well known locality in Oregon whose name I can't remember at the moment. The opals from Spencer, Idaho, rarely display true cat's-eyes and stars when cut as triplets. None of that type are known from any other source.
Getting back to your water question, all precious opals (the ones that show play of color) contain varying amounts of water. When it dries out, say in low-humidity environments, they can craze and break apart. Fine opals stored in bank vaults are very susceptible to crazing because the vaults are kept at very low humidity to preserve paper documents. The rough opals one sees at gem shows are usually kept in water for display purposes only, to show off their colors. The water also magnifies their size and hides cracks and other blemishes. Rule of thumb: always buy your rough opal dry.
Rick, I'm glad you wrote all that so I didn't have to!
Robin
"Of all tyrannies, a tyranny sincerely exercised for the good of its victims may be the most oppressive. It would be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated; but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience."
Interesting info gemfeller , thank you. Kind of a conundrum, they are viewed best in water, and can craze if they dry out, but you'd want to buy them dry. I suppose this isn't unlike buying slabs, I always dry them off to check for fractures, but I wonder if opals might not show fractures until they are very dry as opposed to just wiped off. And people buying opal jewelry likely aren't storing them in water :-) so I've heard the need to wear them often to combat the drying out.
So I have these opal pieces been sitting on a shelf for years. The ones in the jar have been in water the entire time, over a decade. The ones in the baggie which are labeled Australian, and the loose mixed ones have never been in water, that same amount of time. I wonder if I should put them all in water. I don't think these are high end, I think more just something to play with and see if we can get some color out of them.
Post by realrockhound on Jun 24, 2024 12:52:40 GMT -5
The real question here is (for the experienced cutters) did I do good? I’m planning on buying some even more expensive opal. I’m talking $1000+ knobbys of black opal. Getting my skills down on the coober cutting them straight out of the rough.
Interesting info gemfeller , thank you. Kind of a conundrum, they are viewed best in water, and can craze if they dry out, but you'd want to buy them dry. I suppose this isn't unlike buying slabs, I always dry them off to check for fractures, but I wonder if opals might not show fractures until they are very dry as opposed to just wiped off. And people buying opal jewelry likely aren't storing them in water :-) so I've heard the need to wear them often to combat the drying out.
Guess I didn't do a very good job of explaining. Too rushed to go into it all in detail again today. Briefly, it all depends on the TYPE of opal one is dealing with. Ethiopian Welo opal is nearly always hydrophane so you don't get it wet after cutting. Most Australian opal as well as Brazilian is nearly always stable so it can withstand water for display or storage. Mexican and other North American opals differ by locality and need individual study...there are books.
I store all of my opal, cheap stuff to top dollar, dry. If it's going to craze I want to know it before its cut and potentially in a client's jewelry. After I cut stones I usually store them 6 months to a year before I even consider selling them for the same reason. And yes, very dry opal rough shows fractures best because water can penetrate them. Professional opal dealers, with some exceptions, sell opal rough dry.
Opal is fascinating stuff. There's another type called "contra-luz' (against the light) that shows play of color only when viewed with light transmitted through the body of the stone, not reflected. I've run into it only in opal from Mexico and from a well known locality in Oregon whose name I can't remember at the moment. The opals from Spencer, Idaho, rarely display true cat's-eyes and stars when cut as triplets. None of that type are known from any other source.
I just posted a video of an opal from Opal Butte that displays the "contra-luz' fire that you're talking about.
The real question here is (for the experienced cutters) did I do good? I’m planning on buying some even more expensive opal. I’m talking $1000+ knobbys of black opal. Getting my skills down on the coober cutting them straight out of the rough.
Your stone looks very well cut to me. Nobbies are a little different. The color doesn't always show and they need to be "explored" to discover how cut stones should be oriented when color is found. They also have a habit of concentrating color in "wormy' areas: bright opal mixed with opal dirt that often defies cutting. Unless they have "proven' color, they're a gamble. But when it goes right, WOW! Good luck.
amygdule Opal Butte is the name I couldn't think of when I posted. Some I've seen is gorgeous with all the various inclusions contrasted with the play of color -- very exotic.
Last Edit: Jun 24, 2024 13:17:40 GMT -5 by gemfeller
The real question here is (for the experienced cutters) did I do good? I’m planning on buying some even more expensive opal. I’m talking $1000+ knobbys of black opal. Getting my skills down on the coober cutting them straight out of the rough.
Your stone looks very well cut to me. Nobbies are a little different. The color doesn't always show and they need to be "explored" to discover how cut stones should be oriented when color is found. They also have a habit of concentrating color in "wormy' areas: bright opal mixed with opal dirt that often defies cutting. Unless they have "proven' color, they're a gamble. But when it goes right, WOW! Good luck.
Good info. Been watching videos on cutting and trying my best to really understand black opal. When I buy some, I want to have it in hand to examine it wit a Gem torch, etc.. Also planning on buying some books to learn how to grade by color, pattern, etc. I’m at a point where I’ve cut so much other semi precious material that I now want to move up to more valuable material since “in my mind” I feel I’m skilled enough to do so. Probably will buy some cheaper black opal as well just to see how it cuts. Then drop some big money.
Really pretty, even though you can’t show it fully, I can imagine it. Nice cab cut too and pretty good size. Did you have to cut it out of matrix? And, are these opals ones that you have to worry about drying out? I know some they say to keep in water or to wear often. Might be a whole nother topic… I haven’t gotten into opals yet because it seems to require an expertise.
With Ethiopian opal from Welo the problem with water is just the opposite. It's a type of opal called hydrophane, meaning basically it's "thirsty" opal and the play of color disappears when it absorbs water. It usually comes back after a few days when it dries, but sometimes the opal cracks and is ruined. Sometimes it just doesn't come back.
But not all Ethiopian opal is hydrophane, including some from Welo. There are several other opal producing areas there and some produce stable opal. One of the worst for cracking, however, is the so-called "chocolate" brown opal that comes from thundereggs. It has its own beauty but like most "volcanic" opal from worldwide sources, it's very "cracky." Australian opal is generally much more stable and the main commercial types are sedimentary rather than volcanic in origin.
There's also a type of opal I've encountered from Mexico I call "reverse hydrophane." A relative gave me a bottle of reddish-brownish Mexican opal she'd brought back from a trip. It was peddled on the street by kids to tourists. None of it showed play of color. I decided to make a cab from one of the prettier red pieces and as I was cutting with water it suddenly burst in to bright greens, reds, oranges etc. I was excited but the colors, in opposite fashion from Welo, disappeared when it dried.
Opal is fascinating stuff. There's another type called "contra-luz' (against the light) that shows play of color only when viewed with light transmitted through the body of the stone, not reflected. I've run into it only in opal from Mexico and from a well known locality in Oregon whose name I can't remember at the moment. The opals from Spencer, Idaho, rarely display true cat's-eyes and stars when cut as triplets. None of that type are known from any other source.
Getting back to your water question, all precious opals (the ones that show play of color) contain varying amounts of water. When it dries out, say in low-humidity environments, they can craze and break apart. Fine opals stored in bank vaults are very susceptible to crazing because the vaults are kept at very low humidity to preserve paper documents. The rough opals one sees at gem shows are usually kept in water for display purposes only, to show off their colors. The water also magnifies their size and hides cracks and other blemishes. Rule of thumb: always buy your rough opal dry.
I saw some of the Contra-Luz at a sale I was at recently. It was a general craft and art sale, not lapidary. The gentleman that had the stone was Mexican and we had a great conversation. He travels to Mexico to some small villages to buy his stone. He said the Contra-Luz is really difficult to get because there are Asian buyers that have deals with most of the miners and they get almost all of it.
Bigfoot is often called Sasquatch, Yeti doesn't seem to care!
rockbrain Yes, Asians in particular value fine opals much more than Americans. Japan has been the best market for years, and now affluent Chinese have joined them. Americans have bought into a lot of nonsense about opals such as they're "bad luck." That silliness came from a Sir Walter Scott novel called "Anne of Gierstein" who se heroine suffered bad luck after being given an opal -- and from London jewelers after the discovery of fine black opal in Australia who used the same heavy-handed setting methods on them they used for much harder diamonds. They broke, and that was financial bad luck!
Last Edit: Jun 24, 2024 14:58:29 GMT -5 by gemfeller
gemfeller Thanks for the additional info above. Definitely an expertise. I like knowing it should be sold dry. Sounds to me if it’s in water, it’s a risky buy. And I like the idea of storing rough and cabs dry, gives it a chance to craze if it’s going to. Like you said better to know if it’s going to be a problem before selling it.
Post by goldfinder on Jun 24, 2024 17:08:33 GMT -5
That's a ripper of a gem realrockhound! Great cut too. Tons of great info on this thread, I've always had a lot of trouble trying to photograph opal, videos with the opal turning definitely seems the way to go.
I've noticed it's tough to buy quality opal rough online. It seems like most the people who sell rough opal are cutters as well and just sell off the mid to lower grade stuff they don't want they cut. Also pretty deceptive zoomed in photos and videos, gotta check the measurements and weight. They'll somehow make a tiny couple carat chip look huge lol.
Cutting opal is a gamble, but it can be really rewarding. I've got some decent stuff off OpalAuctions but also some junk that looked great in videos but cut nothing. My best luck has been at local sales like Craigslist or people selling off old collections on eBay with bad photos lol.
The real question here is (for the experienced cutters) did I do good? I’m planning on buying some even more expensive opal. I’m talking $1000+ knobbys of black opal. Getting my skills down on the coober cutting them straight out of the rough.
You did good.
I have my opal stored both ways. I haven't had a problem really with cutting opals that have been stored in water and then letting them dry out. If they're going to crack or craze they'll do it pretty quickly. The ones we have stored in gem jars in trays that we have cut and have been in there for years are fine. We found one once that had cracked in there over 5 years ago and we attributed it to probably an internal crack that got really cooked in the sun doing an outdoor show at the Courthouse Square. All the rest of them survived just fine. I don't sell them right away if I cut them from wet rough but I think only 1 or 2 have crazed over all this time. It does depend on what field the rough comes from. There were a few fields that were known to have cracky opal and we avoided that stuff. Most of our rough is Lightning Ridge, Mintabie and Lambina because those were our favorite fields, but I do have Cooper Pedy rough. Mintabie and Lambina fields are both closed now because they were on Aboriginal land and they took the land back. I don't know if much is coming out of the Ridge anymore. The last time we bought any rough was from a dealer in Australia that I was friends with who would sell parcels for the miners. We bought a full parcel (all grades) and got a good deal on it. It was Coober Pedy material, but the top grade stuff in that parcel is really pretty. That was the last parcel Trevor sold before he retired. That was quite a few years ago now.
The opals you currently have dry do not need to be stored in water. If they were going to crack or craze they would have done it already. The boulder opal (looks like Koroit in that tray) never needs to be stored in water.
Normally, using a gem torch on a black opal is going to show you much unless it's a crystal nobby and even then it will be iffy. Black potch is not translucent and you can't see anything unless there is color showing on the surface. Even that will not tell you if the color goes through or if it's just a little patch. It's a total crap shoot cutting black. If you want to know anything about cutting black, let me know and I'll give you my process. Hopefully Gary opalpyrexia can give you his 2 cents, too.
Robin
"Of all tyrannies, a tyranny sincerely exercised for the good of its victims may be the most oppressive. It would be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated; but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience."
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