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EARTH SCIENCE

Platte Canyon High School
Bailey, Colorado

Canyon Room

CONGLOMERATE

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Cobbles and boulders can be seen all around the Canyon Room.  Around the upper terrace and around the base supports for the columns.  Cobbles are the rocks ranging in size from 64 mm (2.5 in) and 256 mm (10 in).  Boulders are rocks larger than 256 mm.  Most of these are cobbles; a few in the Canyon room would be considered small boulders.  Rocks smaller than cobbles, pebbles (2mm - 64mm), are also uncommon in the room.

Granite, a light gray example.
All the rocks used are well-rounded, probably from glacial or river deposits.  Although I do not know exactly where these particular rocks came from, similar rocks can be found south and east of Buena Vista, around Gunnison, and even here in Bailey.  The smooth, rounded surfaces are due to abrasion of the rocks by water-carried sands and silts and by the tumbling of the rocks in rivers and by glacial ice. The types of rocks are quite varied.  You can see several types of granite, amphibolites, quartzites, schists, gneisses, and even a few porphyritic varieties are seen to the right.  

Quartzite
Schist
Large phenocryst of feldspar in this cobble. 
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