Our local source of crazy lace agate is the tin bearing rocks of Cornwall, associated with the granite batholiths there and the edge of Dartmoor. Agates and geodes are mined from the bedrock in Mexico, Brazil and Uruguay. You can see agate nodules in the rock that makes up Edinburgh castle if you look hard enough. Nick Royall
https://orchid.ganoksin.com/t/how-are-agates-formed/40674
The agate is normally formed by a sol gel process at temperatures around 500-600 deg c but can be as low as 100 deg c. This puts silica into a solution which solidifies to a gel then a solid as the temp and pressure drop.
https://orchid.ganoksin.com/t/how-are-agates-formed/40674
Sometimes you can find the source rock for the agates and find them still in place...and difficult to get out...other times they will be found by digging in the soil formed by the decomposed rock. Sometimes the source rock is completely eroded away.
https://orchid.ganoksin.com/t/how-are-agates-formed/40674
Lake Superior agate. 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 in Minnesota, Wisconsin, and Michigan. In 1969 the Lake Superior agate was designated by the Minnesota Legislature as the official state gemstone. The Lake Superior agate was selected because the agate reflects many aspects of Minnesota. It was formed during lava eruptions that occurred in Minnesota about a billion years ago.
https://en.wikipedia.org/wiki/Lake_Superior_agate
The Gemstone Agate. 1  Agate is a banded form of finely-grained, microcrystalline Quartz. The lovely color patterns and banding make this translucent gemstone very unique. Agates can have many distinctive styles and patterns, but each Agate is unique in its own habit, with no two Agates being the same.
http://www.minerals.net/gemstone/agate_gemstone.aspx
The Lake Superior agate is noted for its rich red, orange, and yellow coloring. This color scheme is caused by the oxidation of iron. Iron leached from rocks provided the pigment that gives the gemstone its beautiful array of color.
https://en.wikipedia.org/wiki/Lake_Superior_agate
Over the years talking to people about collecting and tumbling agates from the oregon beach it turns out I have never talked to a person that knows where they came from. Agate is silicon dioxide that can fill any void or crack in rock. Agate can be big sheets or masses but people only see the rounded type polished agates.
https://www.youtube.com/watch?v=ctm0dhhhQ0M
Over the years talking to people about collecting and tumbling agates from the oregon beach it turns out I have never talked to a person that knows where the... Over the years talking to people about collecting and tumbling agates from the oregon beach it turns out I have never talked to a person that knows where the...
https://www.youtube.com/watch?v=ctm0dhhhQ0M
The gas pockets in which the agates formed were primarily small, about 1 cm in diameter. A few Lake Superior agates have been found that are 22 cm in diameter with a mass exceeding 10 kilograms. Very large agates are extremely rare. The most common type of Lake Superior agate is the fortification agate with its
https://en.wikipedia.org/wiki/Lake_Superior_agate
It sounds like in your case the agates are formed in the bubble holes in the basalt flows. This can be called amygdaloidal basalt. When the basalt weathers the agates do not decompose as fast as the host rock does and the agates end up in the stream and river drainage.
https://orchid.ganoksin.com/t/how-are-agates-formed/40674
how is agate formed
The agate is normally formed by a sol gel process at temperatures around 500 to 600 degrees Celsius, but can be as low as 100 degrees Celsius. The agate is normally formed by a sol gel process at temperatures around 500 to 600 degree Celsius but can be as low as 100 degree Celsius. The agate is normally formed by a sol gel process at temperatures around 500 to 600 degrees Celsius but can be as low as 100 degrees Celsius.