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over the summer I have been collecting some rocks along the beach and I wonder if you could tell me what these are.

Hi Brenda,
Very colorful rocks you have there.  Minerals mostly.  Almost all of them are quartz.  That's a silicon dioxide (SiO2# mineral that is very hard and very resistant to erosion.  Almost all the sand on all the beaches in the world are quartz grains.  Quartz is glassy looking and translucent.  It can harbor many types of impurities which tend to disseminate their color throughout the mineral.  Quartz can be clear, and it can be white to black and any color in between.  Agates are quartz and think how colorful they can be #if you can't, then GOOGLE them and you'll see what I mean#.  

These two sites will give you an idea of the many different color varieties you can find in quartz:

There is one specimen that might be an actual rock.  That's the big, yellowish fellow on the left side of the image.  It looks like it might be a metamorphic rock called quartzite.  From the name you might suspect that it has something to do with quartz, and you would be correct.  To get a metamorphic rock you have to add enough pressure and temperature to almost melt it.  That will change the original material.  In this case a lot of quartz sand was deposited in one place, maybe a beach, and then covered over and buried very deep.  The pressures and temperatures created by that deep burial #may be miles) welded together all the sand grains.  Sometimes you can see the grains, sometimes they are so melted together it looks smooth.

This image will give you an idea of a quartzite that looks much like yours:

Hope this helps.


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C. Robert Reszka, Jr.


I can answer any general geology question (rocks, minerals, stratigraphy, geomorphology etc.). My expertise is in the geology of the Michigan Basin, PreCambrian, Paleozoic and Recent. I can answer questions concerning mining and petroleum exploration and production and the laws concerning those activities. I can also answer questions concerning stratigraphy of the Michigan Basin. I will also answer questions about mineral and rock collecting in the Basin. I won`t be able to answer many specific questions on hydrology, geophysics or geochemistry. I may be able to answer very general questions in those venues.


I have been working for the State of Michigan for 36 years as a Geologist and a Resource Analyst. I have experience with Subsurface Geology and Petroleum Geology, mining in Michigan, and Sand Dune Mining and Protection issues.

Michigan Basin Geological Society

Decade of North American Geology.
Bedrock Geology of Michigan

BS Wayne State University

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