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Snapshot geology of the northern Gallatins
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Hyalite opal (SiO2) is an amorphous form of silica that is found coating other rock faces. It has lent its name to “Hyalite National Park,” a recreation area on the Custer-Gallatin National Forest that is sometimes referred to as the busiest in the region.

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Dendritic crystals are perfect illustrations of fractilization. In this case, a supersaturated liquid wicked between two plates of andesite. The rest of the story… I am comfortable leaving a mystery.

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Hyalite-area rock is famously unstable.

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On the south face of Mt Chisholm, strata of basalt alternates with breccia and aborted columns.

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