| 11. | The brothers tried placer mining but soon opened a trading post.
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| 12. | Placer materials must be both dense and resistant to weathering processes.
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| 13. | Quartz mining predominated but there was some placer mining as well.
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| 14. | From Nebraska he moved to the placer mines in the Dakotas.
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| 15. | They mine hard rock deposits and placer deposits left by glaciers.
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| 16. | Miners first came to Butte in 1864 to mine placer gold.
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| 17. | Placer mining had always been hampered by a heavy brown sand.
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| 18. | A Placer County in the California Senate from 1852 to 1857.
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| 19. | Placer mining in the area continued into the later 19th century.
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| 20. | Soon the placers began to run out and the population declined.
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