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| HOME : FORUM : COMMUNITY : Archives : Mineralogy Photo Gallery : Opal Formation |
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Post#1 @
08-12-03
, 12:39 PM
This is a photograph of boulder opal still inside of it's host ironstone matrix. Quite a pretty color, and you can see that opal, formed when molten lava liquifies sand into a glass like mixture and mixes with just the right amount of water (usually 3% to 10% on most gem quality but as high as 20% on stones found under the water table which have a high propensity to crack or craze) will flow through cracks in the ironstone (as pictured) until it can pool together and cool down forming the opal that you see here. This stone was taken from "Coober Pedy" in Australia where most of the worlds commercial quality opal comes from. The quality of the opal in this stone would not warrant it to be cut into gem stones. |
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Post#2 @
08-12-03
, 12:43 PM
Just for reference the stone pictured above and a closer view pictured below measures about 10 inches long and about 7 inches wide and weighs (just a guess) about 5 pounds or so. |
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Post#3 @
08-12-03
, 12:46 PM
This is another (not so great) picture of when opal in it's liquid state took the place of a tree root, so it is in effect an opalized petrified tree... |
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Post#4 @
08-12-03
, 12:53 PM
And if the miner is REALLY lucky, somewhere in the Lightning Ridge area, he or she may find a "knobbie" which will result in a fine "Harlequin" opal like either of the following stones. |
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Post#5 @
08-12-03
, 12:55 PM
.... |
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wow!
Post#6 @
08-12-03
, 01:44 PM
Opal is my favorite gemstone and my birthstone. i didn't know it was formed from lava melting the sand--cool. what makes a "knobbie"--the patchwork type colors? mars |
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Post#7 @
08-12-03
, 01:54 PM
Those are fantastic photos Erik; I always look forward to your posts and photos. Thanks; keep them coming. 
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Post#8 @
08-12-03
, 01:58 PM
A "knobbie" is just a little pocket of black opal found in the ground usually the size of a small rock they are at complete random patterns scattered throughout the Lightning Ridge area of Australia. Anywhere the silica collects to form the opal. The miners will dig into the ground until they find, what they call "Opal dirt" which is a Talc powder like substance which will usually mean opal is nearby. They will then follow this opal dirt horizontally through the dirt and see if they can find these little "knobbies" Opal mining is done primarily by two man teams. There arent any big corporations like DeBeers doing any mining in Australia because the government there will only give any one individual 2 claims (50 meter x 50 meter sections) at a time. I've heard that these claims cost about 50 dollars each. There are quite a few hard luck stories though, for those that want to plunk down the $50 dollars and start digging opals for a living
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Post#9 @
02-06-05
, 08:18 PM
Does any one know what "Coober Pedy" means??????? |
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Post#10 @
02-06-05
, 08:28 PM
I don't know if it's "Coober Pedy"...but I know that one Australian place name is aboriginese for "White Man with a Pick", or something like that. I think that's a riot!  widget |
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Post#11 @
02-06-05
, 08:37 PM
Nice try, its my understanding (and you will probubly get different storys depening on who you talk to" I was told it means "white man in a hole". |
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thanks for the great pics! I love seeing stones in the rough like that, and that little "knobbie" is so pretty! I want one! How much does something like either one of those stones cost? rough idea...I have heard that black opal is really expensive. |
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