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Gemstones, Minerals & Fossils
Lapidary
Anyone treated fairy opal before?
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<blockquote data-quote="Keen Ken" data-source="post: 314156" data-attributes="member: 211"><p>If the opal replaced the limestone wouldn't the whole stone be opalised?,and not opal impregnated as it appears to be under magnification. You can see the sand grains.</p><p>The use of the work "concrete" on the opal fields has been used for decades. </p><p> My guess would be the use of that word has given rise to the <u>thought</u> of the matrix consisting of some sort of limestone, which we know is not the case, else the sulphuric acid would dissolve the "limestone" during the treatment of the matrix.</p><p>I did try the acid-sugar treatment years ago on some Queensland sandstone matrix (like what was pictured). I found the sandstone had a fair percentage of gypsum which dissolved and the sandstone fell apart.</p><p>I do know the commonly used technique for blackening and stabilising sandstone matrix but this process is now under patent (not by me). Not willing to risk my neck here.</p></blockquote><p></p>
[QUOTE="Keen Ken, post: 314156, member: 211"] If the opal replaced the limestone wouldn't the whole stone be opalised?,and not opal impregnated as it appears to be under magnification. You can see the sand grains. The use of the work "concrete" on the opal fields has been used for decades. My guess would be the use of that word has given rise to the [u]thought[/u] of the matrix consisting of some sort of limestone, which we know is not the case, else the sulphuric acid would dissolve the "limestone" during the treatment of the matrix. I did try the acid-sugar treatment years ago on some Queensland sandstone matrix (like what was pictured). I found the sandstone had a fair percentage of gypsum which dissolved and the sandstone fell apart. I do know the commonly used technique for blackening and stabilising sandstone matrix but this process is now under patent (not by me). Not willing to risk my neck here. [/QUOTE]
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Gemstones, Minerals & Fossils
Lapidary
Anyone treated fairy opal before?
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