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Gemstones, Minerals & Fossils
Gemstones and Minerals
Special rock
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<blockquote data-quote="user 4386" data-source="post: 646581" data-attributes="member: 4386"><p>Grubstake is quite correct - granodiorite, It is not what it "looks like" that determines the rock type, but the percentage of diagnostic minerals that make it up - quartz, feldspars and micas.</p><p></p><p>Granite is a slightly less likely possibility (granodiorite and granite simply have different feldspars in them). Both are very common igneous (plutonic) rocks that make up a lot of Australia.</p><p></p><p>In this diagram showing plutonic igneous rock compositions Q= quartz, A = alkali feldspar P = Plagioclase feldspar The percentages of each mineral are written along the three sides. Plutonic rocks crystallize below the ground surface </p><p></p><p>[ATTACH=full]2335[/ATTACH]</p><p></p><p>Here is the equivalent diagram for lavas (when the magma reaches surface and flows out on the ground.</p><p></p><p>[ATTACH=full]2336[/ATTACH]</p></blockquote><p></p>
[QUOTE="user 4386, post: 646581, member: 4386"] Grubstake is quite correct - granodiorite, It is not what it "looks like" that determines the rock type, but the percentage of diagnostic minerals that make it up - quartz, feldspars and micas. Granite is a slightly less likely possibility (granodiorite and granite simply have different feldspars in them). Both are very common igneous (plutonic) rocks that make up a lot of Australia. In this diagram showing plutonic igneous rock compositions Q= quartz, A = alkali feldspar P = Plagioclase feldspar The percentages of each mineral are written along the three sides. Plutonic rocks crystallize below the ground surface [ATTACH type="full" alt="1655956399117.png"]2335[/ATTACH] Here is the equivalent diagram for lavas (when the magma reaches surface and flows out on the ground. [ATTACH type="full"]2336[/ATTACH] [/QUOTE]
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Gemstones, Minerals & Fossils
Gemstones and Minerals
Special rock
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