Sedimentary Rock Week 5

Sandstone

Sand refers to the size of the grains in the rock.  Particles can range from 1/16 millimeter to 2 millimeters in diameter.   The grains of sand in sandstone are small particles of rock, mineral, or organic matter that have been reduced in size by weathering.  They tend to be susceptible to physical weathering.  They have traveled or been deposited by means of water, wind, ice, or biological means.   Once they have deposited they will begin the process of lithification.  This is where the particles cement and consolidate into sedimentary rock.  Quartz is usually one of the most common types of sand grain present in sandstone. They are formed in sheets as the water brings in the sediment and it settles and then the process repeats.  These tend to break into sheets after formed.  

This is the top of the rock.  One thing I noticed in the purple layer, is a few directional waves or ripples.  They seem to be all facing the same directions.  When the rock was deposited the water seems to have been flowing in one direction.  It is also very fine grained and well sorted.  You can see a little white along the sharp edges.  This could be signs of physical or chemical weather.  I happen to know it was from a rock quarry in Virgin, Utah.   The rock companies come in and mine the sheets to sell for landscaping rock.  The remnants are left for people to gather with a BLM permit.  The breakup of this rock would be considered biological and then natural forces would take over.  

My daughter named this the rainbow rock.  I like how you can see the different layers of sediment as they built up to form this rock. 

Bottom and side of the same rock.  You can tell this edge was not broken by mining but has weathering effects.

The bottom side of the same rock.  It is completely different than the smooth rippled top.  It seems like this layer has less sand and larger size and darker minerals.  The pattern of deposition is so interesting.  It seems to be more phyllite in character?  My guess is that it might be Granite?  It is more random and seems to have larger seams that were filled in by the lighter color sediment.