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quartzite - maroon and gray-banded Lower Cambrian quartzite - display specimen

$ 20.00

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This quartzite is from the Emigrant Pass Member of the Lower Cambrian Zabriskie Quartzite. Initially this was nearshore marine sediment that became a sandstone with compaction and lithification. Subsequent deeper burial and metamorphism produced a quartzite from that sandstone, now essentially mashed together quartz grains. The freshly broken surface of a quartzite looks grainy without individual grains being visible.

Quartzite is one of the harder metamorphic rocks. When the continental glacier, over a mile thick, planed off the rocks of what is now Wisconsin, it rode up and over the Baraboo Quartzite and was unable to remove it. Countless geology students have discovered that what the glacier could not remove is not easy for a budding geologist to remove either. 

The Zabriskie Quartzite is Lower Cambrian in age. It retains evidence of bedding in the gray and maroon bands. Ask your students what kind of rock this was before it became a quartzite, and why they say so. If they answer sedimentary, the remnants of bedding is an acceptable explanation. If they answer sandstone, I would accept either the mashed-together sand grains or the bedding, which you might expect in a sandstone.

The field photo shows the outcrop. You would hardly expect to find that the maroon ridge at top right was this quartzite when looking at a fresh surface. The rocks in the ravine are either limestone (gray) or quartzite (maroonish brown). To identify a rock, you need a fresh surface, one reason a geologist carries a hammer. Field assistant is Cucumber, who named herself by being cool as a cucumber when riding in the van.

 

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