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Gold Prospecting
Alluvial Gold Prospecting
Confused about sudden change in deposition layers in creek
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<blockquote data-quote="Sushi" data-source="post: 481099" data-attributes="member: 12342"><p>First picture is quartz with most of the crystal structure intact so you can assume these have not travelled far within the river otherwise they would be a lot more rounded.</p><p></p><p>Photo 3 is a conglomerate. Spot on.</p><p></p><p>Photo 4. Congratulations, you've found sapphire.</p><p></p><p>In terms of the deposits in the river, you have to remember that the process of deposition is happening in what is referred to as 'deep or geological time'. This process of deposition has been happening for thousands and potentially millions of years. The layers of mud/clay/silt are periods of when the river has been exceedingly flooded but without a lot of water movement to allow sedimentation on the river bottom. So you've got lots of water but not enough flow to be causing all the silts on the bottom to be stirred up. At some point in time before the high water deposited silt, Sapphires have formed in metamorphic schists or igneous basalts, and have been weathered out through erosion, likely water in this case, and have been deposited along the bottom of the river due to being more dense. During this point in time you could assume there has been more water flow to push the Sapphires down the stream (assuming they're found in the whole system). As time goes in you've got different periods of flooding and drought within the river causing deposition of different materials. If you found a really good assortment of water worn pebbles in a wash layer, you could even conclude how fast the water was travelling during that point in time due to their orientation.</p><p></p><p>Long story short, you've discovered a number of geological processes in how deposits form in river beds over thousands of years.</p><p></p><p>Also, would love to see a photo of the last specimen with light coming through it. Could be sapphire or zircon.</p></blockquote><p></p>
[QUOTE="Sushi, post: 481099, member: 12342"] First picture is quartz with most of the crystal structure intact so you can assume these have not travelled far within the river otherwise they would be a lot more rounded. Photo 3 is a conglomerate. Spot on. Photo 4. Congratulations, you've found sapphire. In terms of the deposits in the river, you have to remember that the process of deposition is happening in what is referred to as 'deep or geological time'. This process of deposition has been happening for thousands and potentially millions of years. The layers of mud/clay/silt are periods of when the river has been exceedingly flooded but without a lot of water movement to allow sedimentation on the river bottom. So you've got lots of water but not enough flow to be causing all the silts on the bottom to be stirred up. At some point in time before the high water deposited silt, Sapphires have formed in metamorphic schists or igneous basalts, and have been weathered out through erosion, likely water in this case, and have been deposited along the bottom of the river due to being more dense. During this point in time you could assume there has been more water flow to push the Sapphires down the stream (assuming they're found in the whole system). As time goes in you've got different periods of flooding and drought within the river causing deposition of different materials. If you found a really good assortment of water worn pebbles in a wash layer, you could even conclude how fast the water was travelling during that point in time due to their orientation. Long story short, you've discovered a number of geological processes in how deposits form in river beds over thousands of years. Also, would love to see a photo of the last specimen with light coming through it. Could be sapphire or zircon. [/QUOTE]
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Gold Prospecting
Alluvial Gold Prospecting
Confused about sudden change in deposition layers in creek
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