(Cooked) common opal (some points, poor pic sorry)

[Ed Brooks]

I've been finding and making gravel out of some stone, I was told it was common opal. I have found it in many colors from green, blue, grey, black, brown, all from the same place. This stuff is kinda soft, breaks however is wants at times. not really sure how to describe this stuff, I have found it works better with antler(soft flaker). I have been making some points out of it, so I'm happy with this stuff, (it's local and free)
I was wondering if anyone has experience with this stuff?
do I need to store it any particular way to keep the stone. I have seen, that it should be kept in water as it may crack when drying, is this the case?
Thank you for your time. Ed 

[Tower]

I have knapped common opal. It is a little tricky if your used to knapping flint. I found lots of fractures & clay pockets in the stone I was given.  It does make some beautiful points.  I can post some pics if you'd like. 

[Ahnlaashock]

Take some of it, and allow it to dry for a couple of months.  If it doesn't fall apart from moisture loss, it knaps just fine.  It fully supports the conchoidal fracture pattern needed in knapping.  Do yourself the favor of drying it first, so what you do make out of it, doesn't crumble before your eyes later.  I cut a lot of pieces out of common opal, and had a knapper make me a couple of arrowheads out if it in the past.  I talked him into buying a bottle of junk opal, and he found a pinfire black opal in it! 
For storage, many people keep in it a glycerin mixture to maintain the stone and prevent crazing.  A display case is fine, if the pieces are picked up and handled often.  The skin oils offer much the same protection.  If not, then they are usually in climate sealed displays to prevent crazing over long periods of time. 

[Ed Brooks]

Tower I'd love to see what you have in this rock, I will also try to get some pics of my stuff as well.
Ahnlaashock, I have some drying out now, in an unheated shop, need to move it into the house. this stuff is out of a pit that was blasted so it may have more cracks than a piece found on the ground, but it seems to make small points ok for what I can do anyway. Thank you for looking and thank you guys for your replies. Ed

[Zuma]

Heck yeah, Columbia River gem points.
I had a lot of fun collecting small opals in the CA desert. Not knappable size but beautiful.
Crabtree has one on line somewhere. I bought some one time and it was crazed like you all say.
If you have patience you can wedge split some for points. A lot like onyx but translucent.
I would love to see some opal points
Zuma

[Ahnlaashock]

I will go see if I have a suitable piece to play with in back tomorrow.  I know I have large enough, but I don't know about suitable for knapping. 
There are also some varieties out there that are not pure opal, and what you will get out of them, is pure luck of the draw. 

[Ahnlaashock]

This is Australian opal, with just a little bit of color here and there.  I did not take a lot of time with it, and be very careful notching! 
It works very easy, and you have to be careful not to take off chunks bigger and deeper than you intended.  Flakes run pretty good with pressure alone.  I preferred antler over metal.

[lostarrow]

 Just curious , but isn't that kind of pricey stuff for Knapping with? I know there's different grades ,but where do you even find this stuff to knap?  I think it would be awesome to get some , even if  to only make a small pendant  .It's my birthstone.

[Zuma]

Hi arrow,
I have a few chunks back home.
If you can't connect with some before March PM me.
Zuma
 Check out Don's ---Opal Arrowhead Made By Don Crabtree - Lithic Casting Lab.Com

[Ahnlaashock]

Opal with play of fire, is considered a gemstone.   Common opal is not.  I am quite sure you can buy it in large pieces for very little money, and could easily arrange a shipment from a mine. 
That material is practice grade for teaching or testing methods.  One step above common.  Wet, so it looks like it has more fire than it does, that material is 20 an ounce or less, retail, last i purchased any.  Been a while.   Even if you go and purchase some better material for around 4 a gram, you would still be talking about spending little money. 
The knapping is interesting.  Someone taking their time to set things up, could get thinning flakes with pressure pretty easy. 
For common opal in large pieces, you would likely have to order a drum or crate, and wait for the long slow shipping thing.  I likely have a pound or so around, but little of it will be suitable for busting up knapping. 
I once bought some large dark garnet at the show at the Indiana fair grounds, and a local knapper worked little bird points out of those too, but he said each flake was a fight.  There is quite a bit of that material out there that is simply too dark for faceted use in anything larger than tiny stones, and it is pretty cheap also.  Knapped thin, the material is beautiful. 

[YosemiteBen]

Sparrow (Frank from Pataha Wa) had some of that once. I have not seen him on here in a while though. We were going to try to hook up a year or so ago at Glass Buttes.

[Trapper Rob]

Nice points Ed.

[Ahnlaashock]

I cut this slice off the top of a stone I cut many years ago for my mother.  It has been in a tray, in case I ever got a chance to use it as an inlay or something.  It is a little over 1.5 inches long in the picture, and I have already worked the edges, but it is pretty thin.  The flakes run pretty well, so I should be able to keep a decent sized piece when done I think.  This piece might cost you twenty or thirty bucks, but can be found for less than that. 
It knaps very easy, and there is a little trick to it.  Push straight in to load pressure against the edge, and then change the angle until it pops.  The trick, is that you can not let your tool follow through.  It will smash right on through the material.  You change the angle until it pops, but your tool can not move much at all, and then you start over.  Works good enough I wish I could afford a truckload! 
Anyway, here it is with the edges worked.



This is not outside the price range of most, but it isn't exactly cheap either.  The results should be stunning, if i can keep from having to work it too small.  It will definitely require some kind of protective wire frame. 

[Bryce]

Ed would you be willing to do a trade? Opal for obsidian

[Ahnlaashock]

If I had a good piece for the purpose, I would send it, but I don't.  My wife saw the piece I posted the picture of, and it already has a home. 
I have been working some common opal pieces myself, learning the feel, before i try to run flakes across the center of the thin piece.  All I have done on it is form the base and remove a couple of problem areas. 
The first piece I got out yesterday, had small check cracks in it that appeared to be on the surface.  They were much deeper, and each flake would stop at the first crack it hit.  The second was out of the same batch, and knapped beautifully.  I will wire wrap the result. 
Be very careful about loading too much pressure where there is good convexity.  I popped an overshot flake that luckily only took out only a small part of the opposite edge yesterday, without intending to do so, with the antler tine, using pressure.   
I absolutely love knapping it, and will likely order a kilo or two from Australia again soon.  The common material should be dirt cheap.   I will report back on price when I order.   If I could supply myself with opal to knap, I don't think I would ever work anything else.   Not surprising, it was my favorite stone to cut also!