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Gemstones, Minerals & Fossils
Gemstones and Minerals
❓Your Mineral Identification Questions answered here
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<blockquote data-quote="user 4386" data-source="post: 450479" data-attributes="member: 4386"><p>That was the reason for my curiosity. The nickel present would be released during formation of the chalcedony (breakdown of olivine to silica and serpentine etc.), but muscovite (in fuchsite = chromium muscovite) does not break down readily at all but tends to stick around as flakes in the soil, as do crystals of chromite. The nickel content would be elevated in the Mt William rocks sufficient to give a pale colour to chalcedony (microquartz) but is far less than in the ultramafic (olivine-rocks) that tend to form good-quality chrysoprase. I tend to see that pattern in WA also - poor quality over weathering metabasalt, good quality over serpentinite (both rocks tend to be lumped as "greenstone" but the Mt William axe heads that I used to find along the creek between Mt William and Melbourne when I was young were metabasalt = "diabase", serpentinite is too soft for axes (but could of course be associated with metabasalt - I cannot remember details of Mt William, which is no longer accessible). Not trying to prove you wrong, just curious.</p></blockquote><p></p>
[QUOTE="user 4386, post: 450479, member: 4386"] That was the reason for my curiosity. The nickel present would be released during formation of the chalcedony (breakdown of olivine to silica and serpentine etc.), but muscovite (in fuchsite = chromium muscovite) does not break down readily at all but tends to stick around as flakes in the soil, as do crystals of chromite. The nickel content would be elevated in the Mt William rocks sufficient to give a pale colour to chalcedony (microquartz) but is far less than in the ultramafic (olivine-rocks) that tend to form good-quality chrysoprase. I tend to see that pattern in WA also - poor quality over weathering metabasalt, good quality over serpentinite (both rocks tend to be lumped as "greenstone" but the Mt William axe heads that I used to find along the creek between Mt William and Melbourne when I was young were metabasalt = "diabase", serpentinite is too soft for axes (but could of course be associated with metabasalt - I cannot remember details of Mt William, which is no longer accessible). Not trying to prove you wrong, just curious. [/QUOTE]
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Gemstones, Minerals & Fossils
Gemstones and Minerals
❓Your Mineral Identification Questions answered here
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