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Gemstones, Minerals & Fossils
Gemstones and Minerals
unknown find from slatey
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<blockquote data-quote="user 4386" data-source="post: 289296" data-attributes="member: 4386"><p>Because the weathering is so intense to form bauxite, it is hard to find an example which shows photographs of both the bauxite (which is fairly pure aluminium oxide without silica) and the silica-bearing rock rock it formed from - the bauxite often looks like this:</p><p></p><p><img src="https://www.prospectingaustralia.com/forum/img/member-images/4386/1478744452_bauxite.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>However I found one photo - the outer part of this specimen is pure bauxite (aluminium, all the silica has gone). The inner core is weathered basalt in which there is still lots of silica (as well as aluminium). You can see the shape of original felspar (plagioclase) laths in both the core, and preserved as shapes within the bauxite</p><p></p><p><img src="https://www.prospectingaustralia.com/forum/img/member-images/4386/1478744519_bauxite_core.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>This is the fresh, unweathered basalt in which you can see the feldspars - it contains about 48% silica at this stage</p><p></p><p><img src="https://www.prospectingaustralia.com/forum/img/member-images/4386/1478744423_dolerite.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p></blockquote><p></p>
[QUOTE="user 4386, post: 289296, member: 4386"] Because the weathering is so intense to form bauxite, it is hard to find an example which shows photographs of both the bauxite (which is fairly pure aluminium oxide without silica) and the silica-bearing rock rock it formed from - the bauxite often looks like this: [img]https://www.prospectingaustralia.com/forum/img/member-images/4386/1478744452_bauxite.jpg[/img] However I found one photo - the outer part of this specimen is pure bauxite (aluminium, all the silica has gone). The inner core is weathered basalt in which there is still lots of silica (as well as aluminium). You can see the shape of original felspar (plagioclase) laths in both the core, and preserved as shapes within the bauxite [img]https://www.prospectingaustralia.com/forum/img/member-images/4386/1478744519_bauxite_core.jpg[/img] This is the fresh, unweathered basalt in which you can see the feldspars - it contains about 48% silica at this stage [img]https://www.prospectingaustralia.com/forum/img/member-images/4386/1478744423_dolerite.jpg[/img] [/QUOTE]
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Gemstones, Minerals & Fossils
Gemstones and Minerals
unknown find from slatey
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