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Gemstones, Minerals & Fossils
Gemstones and Minerals
❓Your Mineral Identification Questions answered here
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<blockquote data-quote="Lefty" data-source="post: 399392" data-attributes="member: 2976"><p>I have a bit of a broader mineral ID question for someone with geo training - how common is it for a volcanic area of one kind to also contain minor intrusions of other kinds?</p><p></p><p>The reason I ask is because I've come to suspect that three seperate areas of volcanic geology I'm aware which are marked as being of the felsic variety also contain minor extrusions of the mafic kind. All the areas are dominated by pale-coloured, high silica type volcanic rocks and plugs. However, within each of them are what appears to be the remains of cone-shaped plugs - on a very much smaller scale - made of a very dark to black fine-grained rock which I'm sure is basalt or something similar. The soil immediately around these little cones of black rock is different to the soil in the general area - it's a rich red, tomato sauce colour.</p><p></p><p>Does this indicate a high iron content, typical of mafic-type volcanics?</p><p></p><p>My interest is of course the possibility of gemmy things of different kinds being possibly found in the same area. Is it correct that just because an area is dominated by one kind of volcanics, it doesn't mean that it can't also contain other types on a small scale?</p></blockquote><p></p>
[QUOTE="Lefty, post: 399392, member: 2976"] I have a bit of a broader mineral ID question for someone with geo training - how common is it for a volcanic area of one kind to also contain minor intrusions of other kinds? The reason I ask is because I've come to suspect that three seperate areas of volcanic geology I'm aware which are marked as being of the felsic variety also contain minor extrusions of the mafic kind. All the areas are dominated by pale-coloured, high silica type volcanic rocks and plugs. However, within each of them are what appears to be the remains of cone-shaped plugs - on a very much smaller scale - made of a very dark to black fine-grained rock which I'm sure is basalt or something similar. The soil immediately around these little cones of black rock is different to the soil in the general area - it's a rich red, tomato sauce colour. Does this indicate a high iron content, typical of mafic-type volcanics? My interest is of course the possibility of gemmy things of different kinds being possibly found in the same area. Is it correct that just because an area is dominated by one kind of volcanics, it doesn't mean that it can't also contain other types on a small scale? [/QUOTE]
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Gemstones, Minerals & Fossils
Gemstones and Minerals
❓Your Mineral Identification Questions answered here
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