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Lake Superior Agates Tumbled polished collecting gifts jewelry making Crafting 1 pound
Lake Superior Agates Tumbled polished collecting gifts jewelry making Crafting 1 pound
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$44.00 USD
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$44.00 USD
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Lake Superior Agates
1lb Container Tumbled-Polished
Random Assortment may vary from photos.
Lake Superior Agates are truly special! These gemstones are known for their distinctive banding patterns and vibrant colors, primarily red, orange, and yellow, caused by iron oxidation.
The Lake Superior agate is a type of agate stained by iron and found on the shores of Lake Superior. Its wide distribution and iron-rich bands of color reflect the gemstone's geologic history. Based on geological studies, Lake Superior Agates are estimated to be around 1.2 billion years old, making them some of the oldest rocks on Earth.
Geologic History
Lake Superior Agate
More than a billion years ago, the North American continent began to split apart along plate boundaries. Magma upwelled into iron-rich lava flows throughout the Midcontinent Rift System, including what is now the Minnesota Iron Range region. These flows are now exposed along the north and south shores of Lake Superior. The tectonic forces that attempted to pull the continent apart, and which left behind the lava flows, also created the Superior trough, a depressed region that became the basin of Lake Superior.
The lava flows formed the conditions for the creation of Lake Superior agates. As the lava solidified, water vapor and carbon dioxide trapped within the solidified flows formed a vesicular texture (literally millions of small bubbles). Later, groundwater transported ferric iron, silica, and other dissolved minerals passed through the trapped gas vesicles. These quartz-rich groundwater solutions deposited concentric bands of fine-grained quartz called chalcedony, or embedded agates.
Over the next billion years, erosion exposed a number of the quartz-filled, banded vesicles — agates. These agates were freed by running water and chemical disintegration of the lavas since these vesicles were now harder than the lava rocks that contained them. The vast majority, however, remained lodged in the lava flows until the next major geologic event that changed them and Minnesota.
During the ensuing ice ages a lobe of glacial ice, the Superior lobe moved into Minnesota through the agate-filled Superior trough. The glacier picked up surface agates and transported them south. Its crushing action and cycle of freezing and thawing at its base also freed many agates from within the lava flows and transported them, too. The advancing glacier acted like an enormous rock tumbler, abrading, fracturing, and rough-polishing the agates.
1lb Container Tumbled-Polished
Random Assortment may vary from photos.
Lake Superior Agates are truly special! These gemstones are known for their distinctive banding patterns and vibrant colors, primarily red, orange, and yellow, caused by iron oxidation.
The Lake Superior agate is a type of agate stained by iron and found on the shores of Lake Superior. Its wide distribution and iron-rich bands of color reflect the gemstone's geologic history. Based on geological studies, Lake Superior Agates are estimated to be around 1.2 billion years old, making them some of the oldest rocks on Earth.
Geologic History
Lake Superior Agate
More than a billion years ago, the North American continent began to split apart along plate boundaries. Magma upwelled into iron-rich lava flows throughout the Midcontinent Rift System, including what is now the Minnesota Iron Range region. These flows are now exposed along the north and south shores of Lake Superior. The tectonic forces that attempted to pull the continent apart, and which left behind the lava flows, also created the Superior trough, a depressed region that became the basin of Lake Superior.
The lava flows formed the conditions for the creation of Lake Superior agates. As the lava solidified, water vapor and carbon dioxide trapped within the solidified flows formed a vesicular texture (literally millions of small bubbles). Later, groundwater transported ferric iron, silica, and other dissolved minerals passed through the trapped gas vesicles. These quartz-rich groundwater solutions deposited concentric bands of fine-grained quartz called chalcedony, or embedded agates.
Over the next billion years, erosion exposed a number of the quartz-filled, banded vesicles — agates. These agates were freed by running water and chemical disintegration of the lavas since these vesicles were now harder than the lava rocks that contained them. The vast majority, however, remained lodged in the lava flows until the next major geologic event that changed them and Minnesota.
During the ensuing ice ages a lobe of glacial ice, the Superior lobe moved into Minnesota through the agate-filled Superior trough. The glacier picked up surface agates and transported them south. Its crushing action and cycle of freezing and thawing at its base also freed many agates from within the lava flows and transported them, too. The advancing glacier acted like an enormous rock tumbler, abrading, fracturing, and rough-polishing the agates.
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