jamesp
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Post by jamesp on May 30, 2018 18:56:09 GMT -5
I agree with hummingbird. Checked my remaining stash of Aussie Opal chips. They are all about 1/4" by 1/16" thick. No cracks or deterioration. Stored in ziplock bags according to flash. Purchased in 2002. My personal necklaces made between 1988 and 2005 are fine. Rings/bracelets made in the same time frame are fine. My remaining cabs purchased in 1986 are also fine. I have done no special climate control on any of these. Guess it all depends on quality of stones. I purchased the chips for $20.00 for 24" strand from a reputable dealer on Ebay. They even came with a guarantee. Ah, the good old days. My friend used to buy Aussie and it was stored in wet clay balls. It has a thing about moisture. Thinking it may crack when it dries... Our chert down this way is made of silica precipitated out of silica rich limestone, looks killer wet, often drab when dry lest polished. Minerals that change personality when dry irritate. Or bleach in sunlight. I have lots of opal rough. Some is stored in water, some is not. Doesn't matter one way or another. If an opal is going to craze or crack, it will. It really all depends on the water content in the opal and the depth it was found at. When I was actively buying opal rough, there were always warnings from other cutters not to buy from certain fields because it was cracky. Other fields had extremely stable opal and you could buy it without experiencing the heartache of watching all your rough craze before your eyes. Sounds like you guys made some prudent purchases. Sounds like a reputable seller is key. |
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jamesp
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Post by jamesp on May 30, 2018 19:00:42 GMT -5
Ok, so it says 55 carats. 5 carats in a gram -- 5.5 grams total weight. Tiny.
Gee, wouldn't that be 11 grams? Ya had the equation right, but the math didn't work out too good, lol.
A Salem cigarette weighs in at .9 grams. 12 cigs = 11 grams = 55 carats(carrots) |
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jamesp
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Post by jamesp on May 30, 2018 19:15:50 GMT -5
Any thoughts on felspar powder ? It does crush to platelets eventually. Being into both glass and minerals I WILL be fooling around with mixing the two. Small gem grade almandines stayed together but probably had different COE, cracking the glass mildly. silicon carbide 30 grit also stayed together at 1500F in glass but severely cracked the glass, guessing large COE differences. Feldspar powder would probably work ok. If in doubt, I'd heat up the powder (or obsidian or other mineral) separately first to allow any water vapor or outgassing to happen, then reheat whatever survives with your glass mix. I've seen some nice effects with mica and metal leaf that gets mixed and then stretched out. Interesting about the garnet. Was it garnet sand, or a larger piece? Agree that the crazing probably due to thermal coefficient difference, though I wonder whether that might be minimized with a slower annealing phase? Used to love seeing the work done in the glass sheds when I was in school way back when - some famous people came out of that program (wish I had bought more of their work when I had the chance). From a 100 pound bag of #4(about 3mm) grit garnets mined from Emerald Creek Idaho. They use garnets in water filtration for some reason, has something to do with density and sand filters. I was asking a water filtration supply house for 300 grit garnets to use for tumbling. Internet search led to this garnet water filter discovery and the usage of abrasive sized garnets. The supply house owner was curious about why I wanted garnet abrasive. He then mentioned his father had a pallet of 100 pound bags sitting in the warehouse for 30 years. Full of fine gemmy #4 almandines that had been mined out years ago. $25/100 pound bag. I do wonder if they were smaller particles if the glass may not have cracked. Slowing anneal would be the best chance. |
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spiritstone
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Post by spiritstone on May 30, 2018 19:17:27 GMT -5
I found a little bit on preventing cracks in welo or porous opal. Seriously... my lab is just not set up for it.  Super critical drying is a process to remove liquid in a precisely controlled way,similar to freeze drying. As a substance crosses the phase boundary from liquid to gas the substance volatilizes and so the volume of the liquid decreases. As this happens, the surface tension at the solid-liquid interface pulls against any structures to which the liquid is attached. Delicate structures, like biological cell walls or the dendrites in silica gel tend to be broken apart by this surface tension as the interface passes. To avoid this, the sample can be brought from the liquid phase to the gas phase directly without crossing the liquid-gas boundary on the phase diagram by increasing the temperature above the"critical" temperature for that substance while constraining the volume of the system. Super critical drying involves a route from liquid to gas which does not cross any phase boundary but instead passes through the super critical region,where the distinction between gas and liquid has been exceeded and then ceases to apply PREVENTION OF CRACKING IN ETHIOPIAN OPAL www.researchgate.net/publication/298707608_PREVENTION_OF_CRACKING_IN_ETHIOPIAN_OPAL |
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Post by 1dave on May 30, 2018 19:45:26 GMT -5
Tall (up to 11 feet) cone shaped "Cathedral Geodes" come from southern Brazil as I've written about before. in 1957 I was in the little town of Artigas Uruguay on the northwestern border with Brazil where the geodes are more huge potato shaped.    from then on I've tried to understand SiO 2. With rising temperature it changes from opal to morganite to chalcedony, agate, low quartz, high quartz, low trudymite, middle tridymite, high tridymite, low cristobalite, high cristobalite, liquid, gas. On cooling down it sluggishly changes back srtep by step as the dimensions and spacing of the atoms decrease in an odd dance. There appears to be forms of silica at low temperatures that no one seems to have studied. H 2O (water) does the same thing. |
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jamesp
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Post by jamesp on May 30, 2018 19:47:34 GMT -5
I found a little bit on preventing cracks in welo or porous opal. Seriously... my lab is just not set up for it. Super critical drying is a process to remove liquid in a precisely controlled way,similar to freeze drying. As a substance crosses the phase boundary from liquid to gas the substance volatilizes and so the volume of the liquid decreases. As this happens, the surface tension at the solid-liquid interface pulls against any structures to which the liquid is attached. Delicate structures, like biological cell walls or the dendrites in silica gel tend to be broken apart by this surface tension as the interface passes. To avoid this, the sample can be brought from the liquid phase to the gas phase directly without crossing the liquid-gas boundary on the phase diagram by increasing the temperature above the"critical" temperature for that substance while constraining the volume of the system. Super critical drying involves a route from liquid to gas which does not cross any phase boundary but instead passes through the super critical region,where the distinction between gas and liquid has been exceeded and then ceases to apply PREVENTION OF CRACKING IN ETHIOPIAN OPAL www.researchgate.net/publication/298707608_PREVENTION_OF_CRACKING_IN_ETHIOPIAN_OPALPeople have gone to extremes to stabilize this beautiful gem spirit. Quite an involved process. I see the Ethiopian opals started on the gem market in the 1990's. |
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Post by hummingbirdstones on May 30, 2018 19:47:43 GMT -5
Ok, so it says 55 carats. 5 carats in a gram -- 5.5 grams total weight. Tiny.
Gee, wouldn't that be 11 grams? Ya had the equation right, but the math didn't work out too good, lol.
Yeah, just noticed that and fixed it. Like I said, my math sucks.  |
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jamesp
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Post by jamesp on May 30, 2018 19:50:42 GMT -5
Tall (up to 11 feet) cone shaped "Cathedral Geodes" come from southern Brazil as I've written about before. in 1957 I was in the little town of Artigas Uruguay on the northwestern border with Brazil where the geodes are more huge potato shaped. from then on I've tried to understand SiO 2. With rising temperature it changes from opal to morganite to chalcedony, agate, low quartz, high quartz, low trudymite, middle tridymite, high tridymite, low cristobalite, high cristobalite, liquid, gas. On cooling down it sluggishly changes back srtep by step as the dimensions and spacing of the atoms decrease in an odd dance. There appears to be forms of silica at low temperatures that no one seems to have studied. H 2O (water) does the same thing. How on earth do they extract those monsters without breaking them. Some seem delicate, perhaps not. |
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jamesp
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Post by jamesp on May 30, 2018 19:54:46 GMT -5
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Post by MsAli on May 30, 2018 21:54:49 GMT -5
Those are gorgeous!
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Post by hummingbirdstones on May 30, 2018 22:28:33 GMT -5
Whoa! Those would be awesome wrapped around the neck with some cord or a thin kumihimo braid.
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Post by fernwood on May 31, 2018 4:44:57 GMT -5
Nice points.
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jamesp
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Post by jamesp on May 31, 2018 5:46:38 GMT -5
Stan gets credits for those. Sent them to him not knowing if he could pull it off. That melt plate chips squirrelly and chips up down left right all around. He has great control to knap that crap. Don't know how he did it. The big kiln could be set up to mass melt 3 large 18" X 18" bricks 2 inches thick. They could be sawn into many inches of 2 inch slabs, knappers pay $1 to $2 per inch of 2 inch slab 5/16" thick. He wants to give me one of them, which one should I get ? Leaning toward the longer Marion for sentimental reasons. Named after Marion county Florida and was my man cave for 20 years on the St John's River. I won't take one with out trading more melt slabs. jamesp Marion county man cave and collecting grounds for aquatic plant biz for 30 years. Pretty much home to the biggest gators in the world. Desolate spot on earth. 50 years ago the shore was way out in the lake in some places. Shoreline continually being eroded away. Arrowheads can be found up to a half mile out in the lake by snorkeling and probing the sand with a sand fork. Both salt water and freshwater critters in this lake. www.flickr.com/photos/67205364@N06/sets/72157632324991181 |
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Post by 1dave on May 31, 2018 5:56:00 GMT -5
Ya can't fool me jamesp ! Those are ancient Kinderwash points from 21,523.123 years ago.  |
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jamesp
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Post by jamesp on May 31, 2018 6:26:44 GMT -5
Ya can't fool me jamesp ! Those are ancient Kinderwash points from 21,523.123 years ago. I'll tell Stan. Georgia/Alabama has running jokes. Georgia says Alabaman is missing link people. You know, between monkey and man theory. |
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jamesp
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Post by jamesp on May 31, 2018 8:25:22 GMT -5
Whoa! Those would be awesome wrapped around the neck with some cord or a thin kumihimo braid. Had to look kumihimo up Robin and yes as it looks totally Native American. Appropriate lace for these no doubt. I put Stan on a massive deep vein of chert in S Georgia that works like glass. He uses it heavily in his knapping arsenal. It chips like obsidian, rings like a bell when tapped with a hammer. Speaking of opal having water, I can take a large magnifying glass on a sunny day and split boulders of this chert by focusing heat on that material. Boils the water and causes expansion, you here a little TINK, and the boulder is in two pieces. No sledge hammer and no vein cutting shrapnel from sledging it to manageable chunks. No impact fractures propagating throughout. If you throw it in a camp fire it splits violently - 2-4-8-64-256 , like it keeps splitting into pieces that each split into pieces like a chain reaction. Moisture within. Disrupts the boys sitting around the fire pit in a hurry, high speed zing sounds of flakes whistling thru the air at high speeds. |
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Post by rockpickerforever on Jun 1, 2018 7:10:27 GMT -5
Buddy and master knapper Stan did a number on 2 melt slabs I sent   Tough decision to pick one, even though there are only two. They are both beauties! Your friend does great work. Although he had some interesting material to work with. |
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jamesp
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Post by jamesp on Jun 1, 2018 8:25:03 GMT -5
Buddy and master knapper Stan did a number on 2 melt slabs I sent Tough decision to pick one, even though there are only two. They are both beauties! Your friend does great work. Although he had some interesting material to work with. The knappers are an interesting bunch. They are true rock lovers and pursue rocks that are known for their workability. So many true Native artifact materials are used to this day by these artists. Having an ancient tradition is amazing if you consider modern man's choice of materials parallels ancient man's choice. Stan uses a lot of chert from the Fl;int River. I find artifacts from that ~30 mile stretch of chert all over the SE US. It heat treats to pinkish. Chips like glass with less impact required. It all has the same small fossils making ID unmistakable. Probably found 5 -6 right here on my farm almost 200 miles away because I live close to the headwaters of the Flint River. I think those guys canoed more rock than we ship postal service, they had MFRB and LFRB ha. I have never found an obsidian arrowhead out of the 2000-3000 arrowheads I have found in SE US. Not even a chip. I collect the chips too because they are much more numerous. The chips are telling as to their source material. Where do they find some of their materials ? They were much better rock collectors because their chip material is often the highest grade material. The first lapidarian 's to walk this country no doubt. |
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Post by rockpickerforever on Jun 1, 2018 8:31:42 GMT -5
jamesp , when I used to belong to a rock club, about four or five years ago we had a speaker that gave a talk about obsidian, and artifacts made from it. Researchers knew all of the locations it was/is found in the Southwest, and could determine the origin of the obsidian by looking at the points. They had it dialed in! Native Americans would travel far and wide to get the materials they liked the best, didn't just settle for what was closest. It was a great presentation.
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jamesp
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Post by jamesp on Jun 1, 2018 8:50:16 GMT -5
jamesp , when I used to belong to a rock club, about four or five years ago we had a speaker that gave a talk about obsidian, and artifacts made from it. Researchers knew all of the locations it was/is found in the Southwest, and could determine the origin of the obsidian by looking at the points. They had it dialed in! Native Americans would travel far and wide to get the materials they liked the best, didn't just settle for what was closest. It was a great presentation. Picked these up on a couple of acres at a small town near my home. I know where most of these materials came from. If any other color than white quartz for the most part they were brought in from over 100 miles in 4 directionsNESW. Diversity of materials rather amazing. The designs time stamp many of them. Looks to be a site used on and off for 6000 years. That's a long time. Great great great great great great(""""""""""""""") Grandfather probably handed down the locations of the stone. That is not possible in our new civilization. Plus they lived their every minute searching for materials and stomping thru the outdoors.  |
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