YOU HAVE TO HAVE YOUR OWN 4X4 to make it up to my Swordfish Mining private tour fee dig for the logs, but the smaller branches dig we can get to easily in street cars. Not to be confused with the Kokopelli canyon digs. Swordfish Mining has Logs, Twigs, Pinecones, in various mines I own that we tour to. 200$ a day AND WOODS FOR .50 A POUND over the 300 pounds (6 - 5 gallon buckets worth included) a day limit. YES hundreds of pounds, not just ounces. Log rounds are more common here than at any of the open "gem" digs. ATTENDED and BY RESERVATION ONLY. 2 person minimum, due to mileage involved.
Needless to say, the fee digs don't allow me to come dig professionally for clients as a service, I'm too lucky, not dishonest. THEY were NOT wanting a "pro" working for the "novice" fees they charge to dig. Being neighbors , I said no worries, it makes it cheaper on the market for me.
I work hard and find opal for a living better than most others could or would. Established 1994; Swordfish Mining is your friendly source for Virgin Valley opals and information. The fee digs shown on the Travel Channel in "Americas' Best Places to Find Cash and Treasure" were; The Royal Peacock Opal Mine in season 1 and The Bonanza Opal Mine LLC in season 2 with Becky. Leah and I were digging in the opening of the first show and I held one of the black opals displayed. Rainbow Ridge and Opal Queen were not shown.
scale in mm
Face picture stone example of hidden scenes opals. Scale is in mm. Black Opal surrounded by White Opal encased in wood. It shows a little crystal conk around the edges. A note about the crack in the black opal: It has not changed after all these years and does not go into the white precious opal back, which has an even brighter play of color than shown on this Face side.
Opal on wood specimen and gemstones. The 3 stones came out of a layer of opal that wrapped around a limb. They still have the grain of the wood cast in opal on the backs. One has some cracks that were there before cutting and the others have never cracked. The long stone has a strip of common opal down one side. I'm working on getting the stuff out and occasionally have dry Virgin Valley Black Fire Opal for sale in varieties of petrified woods, limb casts, bark chunks, and paleo-botany specimens more than gem rough comes out. The majority of the opals from Nevada, as they are around the world, are white or clear. The black opals are much rarer and most are white or clear over a black background. The white is usually manganese oxide and the blacks usually are tinted by manganese or carbon, at least here where the opal itself is dark, not clear on dark.
A good day digging with satisfied customers and their opals.
Letters of recommendation are on file. Note: I am sorry I can no longer provide digging services for you due to mine policies of principles only. Mr Wentzel has been banned from all the fee digs if you are curious, call and say your are a friend of his and gauge your welcome...NOT warm!
The specimens range from ordinary Opalized wood to gem opal. Some will slab out and many stones have been cut from them. Some won't, but any type of precious play of color can be presented as an enhanced cabinet specimen. They can be sanded smooth first or not, usually not, as that would destroy the bright and usually thin surface films and fossil textures.
Using clear 330 Epoxy, Gel coat, Opticon, or Clear glues; the piece is flow coated intact. Some work and yet others can ruin the piece. Not all pieces react the same to different enhancements. Peacock opal has been know to literally blow up in Glycerin. It's experimentation prior to enhancement that saves a lot of opals. Most enhancements have drawbacks or limitations that have been discovered when all those triplets and doublets were made. Constructed Australian triplets glues failed regularly when immersed often in water and as such they come with warnings.
Harry Wilson, owner of the Royal Peacock Mine Resort, has been quoted by the American Opal Society newsletter as having used mineral oil for drying and then also vacuum for different methods of stabilization. My partner swears it works. Has nice treated black opals for sale. Brett who used to be with them has made jewelry for him. A LOT of specimen collectors swear by oil for eternal preservation and the auzzies curse it as a fraud due to old auzzie sellers oiling cracky opal for sale to cutters. Some opal just goes crazy and white when put into glycerin while it dries others for cutting. Don't ask me why some opals are different from others. I understand that not everything works and some enhancements are irreversible. The only way to make sure nothing changes is to let nothing change; Wet; keep it wet, Dry; keep it dry, Gem; cut and polish. The Village Smithy has a nice description of the process on line already for Opticon.
I have a selection of various wet opals and dried opal for sale. Less than super gem grade stable opals are sold in parcels instead of picking by the gram. They contain good opal and specimens. Some cut solids and others can be used for floating opal pendants in small glass vials.
Typical $1 a gram white opals after being desert dried. The opal that dries out fine without crazing will at least cut small stones. $10 a gram is larger multi-color. $100 a gm for gem fossils and black cutters. Any bigger better opals are sold by the piece if they were not dried to be cut.
The opal forms in a different manner here. It is prepared for sale differently due to the very small amounts ever found. Mainly the damp rough is dried to prove it up and see what is crazy and what is not. You don't just assume it is stable because not all opal is stable regardless of where it was mined. It does not completely dry for cutting until it has been completely removed from the dirt and allowed to dry in air for a period of months. That is my standard for determining worth before retailing. Hobbyists sell only wet specimens due to the high loss rate when drying. You can count on the fact my dry opal has been exposed to desert air for months or years. We don't run it trough a cement mixer to crush up the crazy and expose the color. Not enough for that level of production or need to totally remove the questionable part of the mine run.
Enhancement with a THIN cyro-acrylate fracture sealer has worked to eliminate undercutting in the wood in the opal & woods and prevents chipping due to separating on the stress cracks from drying on the bright but cracked pieces that you want to keep the size or shape of. I will always disclose if I enhanced the piece in any way other than by polishing the stone. In person you can pick from the show "by the gram" tubs. By mail you get an unsearched pour for quantities or pick for small gram amounts. Some pour will be what you'd never pick, but that is the opal sellers parcel method of marketing. I don't treat rough opal.
A 20% Military Discount is subtracted from the product price only, not the tax or Shipping and miniscule handling charges.
I prefer to use the US postal service. UPS excludes unset rough opal from insurance??? Fed Ex gives packages to the post office for delivery to us or charges us $25 dollars just to drive 200 hundred and fifty miles to come get packages.
If you return the opal it must be pre-authorized. Please call first and definitely insure it. Unauthorized parcels will not be signed for and lost parcels never existed other than your insurance claim. The opal received back is inspected before final acceptance and must be all of the same opals received by you without any alteration or substitution. Touch any to a wheel or work on it and you are working your opal parcel not mine. Return the entire parcel completely UNCHANGED within 1 week of your receipt at your expense and risk and I'll gladly give you 100% store credit or cash refund less costs.
The opal can't have been cooked, de-pressurized, pulled into every little piece, cut on or windowed, or high graded (stones switched) as this is theft and violates the whole all or nothing parcel concept this industry of trust has been founded on. Also we keep photo records. Soaking and baking the dry opal is considered alterations. Without insurance you will only be paid if I receive the exact same opals back. Theft is not allowed. We usually clear up any questions with a phone call so you really should call first. Pacific Time Zone please. BEFORE you buy it.
100% money back less S&H if ya just don't like it. Rather make you happy out of the store now that your questions have been dealt with.
When you receive this parcel of bone dry rough, YOU CAN NOT dump it all into water and then expect to try and see how it looks polished or even weigh it to see how much it weighs now. Look at it dry, that is what it will cut out to. Some opal will break when re-wetting if it hasn't been cut reducing it's dimensions. If you cut it dry this will not happen unless you overheat it. If so it will crack like others opal will. You can wet it, but the opal can pick up over 10% additional water weight and usually changes opacity and the play of colors. That soaking may work with other opals to sell you water, but not dry Virgin Valley opals. You can dip the opals one at a time to look at them, but shake off the excess water & set them to dry back off when done looking at each piece. This way they still look as good as they will when cut. I will not accept opal back because it looks different wet; you have to re-dry your opal to see the dry colors again, as all not ground away opal will be dry back brighter. Once you start experimenting on your opal you are working with your opal. I won't take back saturated opal as what was sent you. If you can't afford the risk, don't take it.
If you dried out a wet specimen and it was one of the majority that will crack some (or craze a lot the first few days of drying) when dried, Well... you broke it after you bought it, so you can't return it. I'm very clear on the prospects for the opal in the selling policy. I do not promise the water will never leak out of your domes. Reasonable care must be taken on your part. You must do the minimum of care at least. I keep my best in another jar so it can't dry out even if it's seal leaks. The jars in the vaults are triple bagged with water layer. If it doesn't match my picture, the count, and the weight, I reserve the right to let you know how exactly the parcel was changed and charge for S&H prior to returning it to you. I don't test dry wet opals prior to shipment and will not be held accountable for any wet specimens ability to dry.
I'm not rich, so I can't afford to be giving rarely found opal away to thieves or let novices experiment on mine without purchase. Outside of the rules of look but don't touch, you are responsible. I want your business and accept criticism where due. I also reserve the right to refund your money once and then never do business with you again. if you are a weasel or involved with criminal activity. Refer back to I'm a nice guy and want your business statement if the last statement bothers you.
My $10 a gram tub when it was first made. Conks usually land in here because the wood is porous. Most conk needs enhanced to be hard as a gemstone. Now I'm working out of a smaller amount that is being refreshed as stuff is declared dry as a bone. These are small solid pieces that will cut gemstones. They have multi-color fire and are not crazed. Some do have cracks and some are just that bright of limb specimens. OZs never build up to be kilos. Sold. If you would like to be put on a waiting list for new opal parcels please drop me a line.
The Virgin Valley Mining District also produces small amounts of a pleasing rainbow of common and semi-precious opals. Swordfish Mining has the fine vein nodule common jasp-opal in a red, yellow to green creamy pastel colored opaque opal. The hardness ran from opal to jasper. The colors of muted pastels are both flat and swirled. Very nice patterns. Sold Out of rough to a overseas buyer other than my persy rough to make gemstones from, cabs will be offered in Goods.
I have some select pieces of bright green fluorescent opal from the Royal Peacock Mine. It appears white to lime green in ordinary light but under long wave ultraviolet light (poster lights) it glows as bright as Williamite from Sterling, NC. That is to say it lights up like a green glow stick. It is slightly radioactive and should be kept in a display area away from small children. I hand pick great shelf and sample pieces for $20 a pound plus S&H. Note this large material all has typical opal flaws and mining/drying cracks to cut around (FROM THE MINE). All nice specimens are limited and are what usually sells at shows. I have no large selection to be making catalogs. Note. You should go direct to the other mines for their materials, but don't forget to compare price, service and value in your purchase consideration. If displayed in the direct sun it will crack some and brown with age, but not inside.
Swordfish Mining has common opalized woods in a lavender, cream, brown combinations and it can be precious. White opals in wood along with the others, such as the charcoal woods, and gypsum or Zeolite limb casts. If you wish larger pieces of Opalized wood shipping costs become a major consideration. We have car and truck load sized pieces. Again these are our rare Virgin Valley opal woods not the relatively common agate and jasper ones. These are opal ore and the inside is a guess until cut or worked down. This will be mined to order. It is not on hand in large amounts.
CACHALON OPAL (or Water Seekers) are also commonly found. This rare precious type of opal appears as a common white precious opal when dry. (good pink green multicolor under diffuse artificial light and stronger outside) Measuring 14.6mm x 9mm x 3.7mm it weighs 2.21cts dry.
soak it (or swim) for 10 minutes and presto' a crystal opal with BRIGHT colors. That you can see thru if it weren't for the colors. $106
It weighs in at 2.32 CTS now. To return to the white opaque opal look takes 30 minutes. The stone has not been treated in any way except being polished. The back is natural and not smooth and has a natural cavity like so many other stones available on the open market. Invisible when set.
I don't normally sort these out as a category as the cachalon is mixed in with the parcels of white opals when they were sorted dry. I note their quality when they were being cut as bright white opals for our own use. Now when you cut "water seekers" the opal goes clear in a short amount of time and the play of color usually disappears totally just like Wollo (Welo Opal). Once dry they sometimes will crack when re-wet. In the fields you can test this by placing the opal against your tongue. A cachalon opal will stick to your tongue and stay there. Usually they can do this over and over but a lot of clear opal when first found will also white out but it will not go back to clear when re-wetted.
Perhaps 15% retains bright colors when saturated. When removed from water the gemstone immediately starts to dry back out. Now if that had been dirty, greasy, soapy dishwater, or shampoo it was immersed in, there could be residue left inside the stone that might interfere with the play of color. Hence the industry warnings from Australian sellers about normal opal care. These stones have a more open atomic structure and actually can sometimes be washed clean again by repeated immersions in clean water.
When it comes to opals in wood, the amount of enclosed precious opal enters into what the piece is worth. Dollar branches are the start of well defined twig casts with no opal at all to super gem opal in all combinations of wood, cones, and cavities up to $1000 a gram. There are over a hundred and twenty plant species identified that were opalized here according to Dr. Munzing.
The parcels are your opportunity to be the grader for your re-selling. Like most Australian parcel sales there is a spread of quality and is sold all or nothing to save the sorting and grading every piece. If it is bought on inspection, or memo, you can pick pieces but at a much higher price which is stated up front by the dealer. We parcel in the post & picks in person. This stuff is rare there is not a lot produced each year for the demand.
Tops conk is gem bright pure opalized matrix in black wood structure skin to skin and is commonly set in fine gold jewelry. Half of the miners time is in the grading of the opal or actually finding that one small outstanding piece that is worth more than all the rest. That's why parcels are much cheaper than pick by the gram or single pieces that are the tops stones that are sperated at the mine when found.
The price for SLABS depends on the opal quality and the solidity of the wood. I have never seen anyone selling slabs that have decent color for less than one hundred of dollars an ounce. Swordfish Mining has grain fire (salt & pepper) to total replacements displaying multiple kinds of play of color in various colored woods and opals. Under $10 a gram woods need treated with a fracture sealer or made into doublets with quartz caps (particularly for use in belt buckles and men's rings).
Extremely rare gem bright Crystal Conk is sold by the piece due to quality and again can retail for over $1000ct. That's over $140,000 an ounce if the gemstone weighed an ounce and you actually sold it for that (larger stones than 15 cts are always discounted off the price for good jewellery sized stones) but you'd never realize that many carats in most rough. Usually cutters grind away 3/4 of the stone just to polish that cabochon.
Most of the best "killer rough" is Individual stones that are priced higher due to their great rarity. Single gem fossils can also sell for more than 1000$ a gram. See good Australian clam prices versus the whole dinosaur that had to be donated to a museum to realize it's true worth. We can not and do not ask that much for ours. Each wood piece is an individual unto itself and we can't guarantee what exact species it even is, what is inside, the hardness or suitability for treatment, without having slabbed it up to see what is inside each one. At that point I usually finish polishing them.
Hong Kong, DEC 27, 2012 –The Gemstone Industry & Laboratory Conference (GILC) formed an Opal Committee task force at their general meeting in Tucson FEB. 2012. Its purpose was to find useable nomenclature as could be applied to the newer hydrophane opals currently on the market. The GILC has determined that disclosure regarding this variety of opal coming from the Wollo district of Ethiopia be as follows:
Type 1 Precious Opal – Hydrophane
Special Care Required:
Hydrophane generally indicates a material that is absorbent when immersed in liquid.
Keep away from cleaning agents, perfumes, oils and any liquids as they can be absorbed and may alter color and/or appearance.
Avoid sudden and extreme temperature changes. Avoid steam and ultrasonic cleaners; clean with a soft cloth.
Black common opal stable dried potch is priced at $15 a ounce. A few well made specimen black potch opal limb casts are available and are sold by the piece as cabinet specimens for collectors. If an opal (not ours) only shows red/orange crack fire it is unstable an unusable. Most black potch from the big mines will not hold together due to carbon or manganese inclusions.
DRYING FACTS: WHY VIRGIN VALLEY OPAL IS MORE EXPENSIVE DRY
Not all opal can be dried out regardless of what country it was mined in. Every mining district has opal unsuitable for cutting. (Refer to the Australian discussions of unstable mines and what levels are stable in the different mining districts.) After saturating the rough and desert drying it with no particular care, I find that if the opals are stable they don't craze and then they can be made into someone's gold jewellery just fine. If they will craze they do and are eliminated. You can baby rough to a gemstone but it will probably crack in the future if the polish is breached.
I've seen a National Geographic television program where the Australian opal dealer was watering the wheelbarrow loads of opal on the ground with a garden hose as he says "Everybody knows you can't dry opal in the desert". Must have been a cracky layer from those not talked about miners, but maybe not. We keep it wet until it is sold or sent to the coastal cutting factories. That was in Australia and I am trying to find my copy for the broadcast date.
I've cut stones out of the stable opal pieces that remain after drying. When we find our opal the clay usually is still stuck tightly to it. Some mines' clay falls right off in water and in other mines the clay or ash has to be ground off. To remove the clay I saturate the mine run in water (which will dissolve any soft absorbent wood and opal pieces into pulp and free the opal veins and also insures when it is dried it will crack then if ever.) until the mud softens and we can scrub it off with a stiff nylon brush.
I look at what kind of wet color and sort it onto a drying rack or for wet specimens. It is then dried exposed to outside air in a metal building for a month or so until "desert cured". This process with associated temperature swings when dying starts crazing in most any opal that will craze. The only opal the old guys here threw up on their roofs was the POTCH to see if any was cachalong and to keep thieves away from it until checked. All the gemmy stuff was protected from the "crows" all too common.
I then select any pieces that show precious color from the "tailings" which is the "potch" or common opal and petrified woods. Then the gemstones are shaped and polished on a Diamond Pacific Genie or Pixie. They are then allowed to re-dry on the top of the pixie. I like to think these ultimate opal torture tests do in all the crazy opals that might have cracked years down the road.
I'll concede some of my miner friends cut their opals right out of the water and they swear they get a larger carat return by weight than if they let it dry out first. I can believe this, as after cutting there is less stress in the stone by there being less stone to stress the piece. There's about as many tricks to cutting gemstones as there people polishing or mining sources used. But there are only so many gemstones in the showcases.
After cut and proven these tough gemstones can be displayed in the direct sun without having to hide them in the shade because they might crack. (See my statements on keeping their opals wet until cut in high humidity coastal towns without the stones ever really be dried completely.) I have never heard back that one of our stones crazed or cracked since being purchased. We believe the best thing you can do for an opal is wear it often, but carefully so as not to break it by contact.
Once dried, the majority of Virgin Valley opal DOES NOT CRAZE later. It usually has cracked into smaller more stable pieces exposing the color faces like all opal does from any countries when mined before sorting. Dried Virgin Valley opal cuts just like any opal. It was formed in beds of Montmorillite deposited on ancient shorelines. It isn't thinly banded color layers, small gas bubble cavity's, or a crack filling film like most volcanic opals. SWORDFISH MINING HAS CUT STONES FROM ALL THE MINES HERE AND I OFFER DRY ROUGH FOR SALE.
The largest stones seem to come from the cores found inside the casts rather than the whole cast being cuttable as it comes out of the ground. The brighter stones seem to come from the thinner films overlying the cores (or centers) that we call rinds; like a watermelon. The opal seems to be directly less stable in relation to its diameter i.e. the bigger the stone the more dry pieces you are going to have when dried. It is the exception to dry unchanged. The rarest are eyes or ghosts with different layers of opal or bubbles in the stone with the same or differing plays of color. Seldom are all levels stable.
This could also explain the claims that you cut the opal real thin wet (such as triplet preparation) to make super bright opals. I haven't done this personally but, I have seen this done by "Doc". He is an old time triplet and doublet cutter who specialized in Virgin Valley Opals and there are several younger active custom jewelry makers. I've also seen a neat little trick where Virgin Valley crystal opal is the cap on other bright triplet or doublet base material instead of clear quartz to make "100%" opals.
I find that a small percentage of Virgin Valley opal mine run gem opal is STABLE from the start. Around 30% of the raw output will craze toward small (floating opal pendant or composite inlays rough size) real fast in the drying process. The opal that crazes slow will still have those initial cracks in them (just like lightning or piled up conchoidial flakes). The other half cracks up holding its structure and is a candidate for fracture sealing. The opal that crazed is passed over to start with. From this sorting with screens we get our bright crystal chips that is used in floating opal jewelry.
Opal Cure (I distribute Opal Cure for 20 plus S&H ground) this 2 part poly ethylene resin works better on opal if they are soaked long and warm enough to lose water content. Say 200 degrees or more. The cyro-acrylates such as Star Bond, Super T, or even Hot Shot do a fair job of fracture sealing but water is a catalyst to make them harden so the piece to treat must be dry first and penetration is usually poor. Some pieces treat well like turquoise does and others can only be sealed by a flow coat. Several processors both in America and Germany are accepting Virgin Valley opal for treatment. And yes some is hopelessly doomed to always slowly crazing and having to be repolished.
We sent semi-dry white gem rough to be commercially cut and when returned, it gave us about 30% return by weight in standard shapes. It was commercially cut in pre-communist Hong Kong. On return we found the most common flaw was HEAT STRESS CRACKS on the points of pears and marquee cuts, probably from careless polishing allowing excessive heat buildup in the stones. Use lots of cooling but not cold water when polishing. Unfortunately the next pound of gem we sent "disappeared" and cured us of trusting even large outfits for commercial cutting.
The Virgin Valley Opal beds are still wet in most cases like many "levels" in Australian mines. This allows for very large opals to be recovered intact without having to grind off sandstone or rock. For those big, bright, black, glassy specimens that have never been dried; there is no guaranteed process to stabilize the stones into gemstone cutting rough. Some believe that slow even drying in the dark over the course of 5 years will save 95% from crazing. Many miners have pet methods to achieve this slow dehydration, not bomb it as fast as it can dry right out of the beds it was sleeping in. The most reliable has been semi permeable low density polyethylene sealable canisters.
Some opal from out here is perfectly stable to cut stones from wet rough. A stabilization process that returns over 85% dry cuttable gems from wet rough would really interest every opal miner. Opal displays it's true nature real quick. Keith Hodson called it "An Honest Opal"; It does what it is going to do, crack or not, if left alone for awhile to dry. When that happens you will see the ads wanting your wet opal for a song.
One of my favorite cracking stories is about an 1 1/2" splinter of a vein that had weathered out of its wood. I had found it out in the old tailings on the hot dust in the sun in the middle of summer. Real nice color even if it was less than 1/4" wide. As I walked the 30 yards to show it to Leah It cracked pop - pop. I heard it, Then it was in 4 pieces. Well, they never cracked again and I polished each of them and now only have 1 left unsold. If it cracked as it got moisture from my hand, it never did again as it was being cut in water.
An opal will crack until the internal surface tension is less than the cohesive force and then it will not crack again unless it is smacked on a hard surface (like most opals are broken). A tight metal setting also can contract with cold and crack opals like a nutcracker. We prefer to see opals either bezel set or with lots of prongs and some physical protection.
Some scientists think opal has a range of molecular structures that are responsible for the toughness of the gemstone. I think we have ALL the range intermixed in the fields out here due to the wide variety of chemistry of the different deposits. The good with the crazy. I fracture seal opal specimens for toughness and crazy or cracked cabochons for visible cracks. I declare all treatments used on a gemstone. By the way most diamond, sapphire, emerald, and ruby resellers DO NOT disclose that most of their stones HAVE been treated in some way. See industry disclaimers from such as GIA assuming most gemstones are treated as much as possible (heat treated, oiled and dyed, or feathers filled).
The petrified wood usually holds the opal into shape for easy fracture sealing. The Opalized wood is as hard as the sealant around the opal, which is still untreated opal, that the cutting exposes to air. If you want to encase the stone you have to polish that outside surface. We find the stones look best polished off just leaving the fracture sealant in openings. A loupe can easily detect these raw edges. Not all opal needs treated. Most is not treated in any way.
The high water content can be slow in leaving. Some crystal opals will go opaque when dry. Called CACHALON or water seekers. These need to be looked at well prior to cutting or they saturate quickly losing the finished color and go back to the saturated play of color which is different when it is dried i.e. clear wet and white dry. Not all stones will do this. Welo opals have an additional white stage where no color is seen until completely re-dried. Virgin Valley does NOT have that property. So, up onto the Pixie, then the next day they are back to what they were dry; proving again they can take a drying without cracking after having scratches on the surface. This also accounts for the quality and longevity of our finished stones if I'm not mistaken.
Just an ordinary parcel of Virgin Valley opal will weigh about 10% less than wet material because of water weight. Not all of this is soaked in it is in the wood and on the surface and the scale bowl besides being in the stone. These water seekers usually are tan or off white when they dry. I have a small amount of tumbled tan potch cachalon and a few grams of separated for cachalon behavior rough to go with the cut gemstones from this material. There is no black cachalong. Brown or gray is as dark as it gets. Black is the least stable.
Almost every opal that has ever been cut up out of a piece of a larger vein, or chunk, or piece of wood, or broken opal mass that was found by seeing a broken face. Knobbies and clams or cones and limbs are some of the exceptions to the rule found by recognizing their distinctive shapes. We get opal so hard it has to be broken or ground with abrasives to see what's inside.
The opals are complete casts with surface features, not just another piece of a crack vein network enclosed in matrix. Most opal that hasn't been broken into smaller pieces yet and has some flaws that it needs to be in smaller pieces before cutting flawless stones.
Part of this problem is attributed to varying density of the different opal layers having different rates of shrinkage when drying. You can usually either cut the inside or the outside of this kind of opal when it has color in both types of opal. Only when it dries will you know if it is, or wasn't, cuttable. If it is going to craze, it will almost always let you know within the first year after final polishing. High altitude, hot dry summer heat and hard frozen winter, define the "desert drying" environment up here.
I don't have "birth dates" on stones because hardly anybody even thinks of that and each year the new stones are placed into a case in the traveling rough display to dry all year (for handy showing of what was cut off what) before going to the shows. I usually select the ones I'll wire wrap and the rest are graded into our gemstone selection displays. Each stone has been air dried prior to your seeing it. OR like in Quartzsite, it goes right off the pixie into that tray in the desert dry air and sun. They rarely crack because they came from dried rough.
All the claims and Fee Digs have a different character to the opal either in form, back ground color and opacity, play of color, patterns of fire. We can usually tell where opal rough was mined by a looking at it. All the mines might produce black opal, white opal, crystal opal, and fire opal, by themselves, or in any combination with woods. The differences can be subtle or quite distinct. I've actually had high graders lie to my face they did not mine my distinctive opal out of my mine without permission claiming it came from a pay dig. I've seen more than one scammer try to sell claims the same way, ot the claims behind them contaminated on the surface with salted fee dig material.
Microcrystalline Opal CT on carbonized wood from the Royal Peacock Mine. Photograph by G. Mustoe at Western Washington University Geology Dept from samples we provided.
Note: all text and photographs copyrights reserved by John Church.
Re-publication not for gain is permitted with proper URL credit given.